Immunobiology: The Immune System in Health and Disease 
By Janeway Charles A, Paul Travers, Mark Walport, and Mark J Shlomchik
With an introduction by Walter Sorochan

Posted December 11, 2021.

 

Introduction to immunity
By Walter Sorochan

 The Communicable Disease Center encourages everyone to get COVID vaccines and booster shot as well. But millions of people are reluctant to do so. Why are they reluctant to get a vaccine? What is the problem?

 Many feel it is their right not to be vaccinated. Others do not believe that the vaccines will not prevent getting infected; indeed, these are part of the thousands who have died! Research author Walter Sorochan believes that the  majority of Americans do not understand how their body immune system works. If they did understand how the covid vaccine is made, then they may be more prone to get vaccinated. The federal government has done a terrible job of informing people about all of this. The purpose of this article is to provide scientific information about how the human body immune system works.

 The immune system is complex. The immune system is a collaborative effort by the entire body to maintain the blood in a "clean" state; the result is immunity --- that is to say; an ability by the body to protect itself from foreign invasion by organisms or substances that might compromise it. Immune theory & dig sys

 Immunity is medical term that describes a state of having sufficient biological defenses to avoid infection, disease, or other unwanted biological invasion. Immunity involves both specific and non-specific components. The non-specific components act either as barriers or as eliminators of pathogens to stop infection by micro-organisms before they can cause disease. Other components of the immune system adapt themselves to each new disease encountered and are able to generate pathogen-specific immunity

 We have been told that it is the bones and lymphatic system, white blood cells, macrophages and T-cells makeup the immune system and are the major protectors of the body. But as the illustration below shows, there are many body organs involved in the immune system. The major organ not included in the illustration is the colon and it's bacteria.

immune all

 Immunity Types

 Immunity to a disease is achieved through the presence of antibodies to that disease in a person’s system. Antibodies are proteins produced by the body to neutralize or destroy toxins or disease-carrying organisms. Antibodies are disease-specific. For example, measles antibody will protect a person who is exposed to measles disease but will have no effect if he or she is exposed to mumps.

 There are two types of immunity: active and passive:

    Active Immunity results when exposure to a disease organism triggers the immune system to produce antibodies to that disease. Active immunity can be acquired through natural immunity or vaccine-induced immunity.
    • Natural immunity is acquired from vaccination of killed or weakened form of disease
    • Vaccine-induced immunity is acquired from vaccination with killed or weakened form of a disease.
    Passive immunity occurs when a person is given antibodies to a disease rather than producing them through his or her own immune system.
    • A newborn baby acquires passive immunity from its mother through the placenta.
    • People can also get passive immunity through antibody-containing blood products such as immune globulin, which may be given when immediate protection from a specific disease is needed.

    The major advantage to passive immunity is that protection is immediate, whereas active immunity takes time (usually several weeks) to develop but is long-lasting. However, passive
    immunity lasts only for a few weeks or months. Vaccine-induced immunity is acquired through the introduction of a killed or weakened form of the disease organism through vaccination.
    Either way, if an immune person comes into contact with that disease in the future, their immune system will recognize it and immediately produce the antibodies needed to fight it. Active immunity is long-lasting, and sometimes life-long.

    Natural immunity occurs through contact with a disease causing agent; when the contact is not deliberate, whereas artificial immunity develops only through vaccinations. Both natural and artificial immunity can be further subdivided, depending on the amount of time the protection lasts. Passive immunity is short lived, and usually lasts only a few months, whereas protection via active immunity lasts much longer, nd is sometimes life-long. The diagram below summarizes these divisions of immunity.

    Immunity22

    Herd immunity is a form of protection that occurs when people in a community become immune to a disease,” Dr. Evans says. “Herd immunity protects the individual and everyone else in the community.” The basic idea is that if enough people in a single community, or “herd,” have the antibodies needed to protect against a particular disease, that disease will have a hard time spreading from person to person. This is important because some people in the community are especially susceptible to diseases, such as babies and young children, the elderly and those with compromised immune systems.

    Herd immunity only works if enough of the population is vaccinated [like 80+ percent or more], either through previous infection or vaccination. It’s easy to assume that everyone else has antibodies, so it doesn’t matter if you receive a vaccine or not. But when enough people make this type of assumption, the community as a whole will struggle to reach the herd immunity threshold, leaving space for infectious disease to continue spreading through the population. Some persons may not be vaccinated, may be infected and display no symptoms [asymptomatic]  but still be able to infect others. This is what may be happening with coronavirus in United States.

    Colon bacteria can determine level of immunity: Researchers since 2000 have discovered that there are over 400 good and bad bacteria living in the large intestine or colon. If the normal balance of 80 - 85% good and 15 - 20 % bad bacteria is disrupted, then the bad bacteria multiply and can cause many of our illnesses and diseases. Today, most of us show the reverse ratio or that of 80% bad and 20% good bacteria. Thus, it’s no coincidence that the incidences of chronic and degenerative diseases have multiplied dramatically since World War II. Affluence has provided a meat and potatoes, cheeseburger, French fries, coke and junk diet that also feeds the colon bacteria that dramatically lower the immune system. This makes most persons susceptible to infection and chronic diseases and especially viruses. Most important, the immune system is compromised! The most compelling evidence comes from Dr. Michael D. Gershon, chairman of the Department of anatomy and cell biology at Columbia University, in his book "The Second Brain," published in 1999.  Gershon: The second brain

    So how does the body keep the bacteria in the colon under control and the immune system high?  The answer is food that feeds both your body and the bacteria in the colon. People who love to eat what is referred to as comfort food --- like milk shakes, soft drinks, white breads, white pastas, cookies, sweets, fries and hamburgers, promote the growth of disease-causing bacteria in the colon that cause a low immune system.   Walker: Cure for Crohns Disease Ewers: Inflammation

    We need to make wiser food choices to improve the immune system and have natural body immunity against viruses. Vaccines are of secondary importance. This is what the federal government is not telling people. We should be focusing on changing from the Standard American Diet [SAD] to eating more vegetables and fruit and also testing the immune level of people before vaccinating them. This is not being done!

    What is immune system; By Bruce Lipton : Length = 32:42 mns.

If you want more specific information about immunity, then you should read the medical version below: 

The components of the immune system:  Janeway: Book Immune system in health & disease 2001

The cells of the  originate in the , where many of them also mature. They then migrate to guard the peripheral tissues, circulating in the blood and in a specialized system of vessels called the .

1-1. The white blood cells of the immune system derive from precursors in the bone marrow

All the cellular elements of blood, including the red blood cells that transport oxygen, the platelets that trigger blood clotting in damaged tissues, and the white blood cells of the , derive ultimately from the same progenitor or precursor cells—the hematopoietic stem cellsin the bone marrow. As these stem cells can give rise to all of the different types of blood cells, they are often known as pluripotent hematopoietic stem cells. Initially, they give rise to stem cells of more limited potential, which are the immediate progenitors of red blood cells, platelets, and the two main categories of white blood cells. The different types of blood cell and their lineage relationships are summarized in Fig. 1.3. We shall be concerned here with all the cells derived from the common lymphoid progenitor and the myeloid progenitor, apart from the megakaryocytes and red blood cells.

Figure 1.3 All the cellular elements of blood, including the lmphocytes of the adaptive immune system, arise from hematopoietic stem cells in the bone marrow. These pluripotent cells divide to produce two more specialized types of stem cells, a common lymphoid.  (more...)

The myeloid progenitor is the precursor of the granulocytes, macrophages, dendritic cells, and mast cells of the .   are one of the three types of phagocyte in the immune system and are distributed widely in the body tissues, where they play a critical part in . They are the mature form of monocytes, which circulate in the blood and differentiate continuously into macrophages upon migration into the tissues.  are specialized to take up  and display it for recognition by . Immature dendritic cells migrate from the blood to reside in the tissues and are both phagocytic and macropinocytic, ingesting large amounts of the surrounding extracellular fluid. Upon encountering a pathogen, they rapidly mature and migrate to lymph nodes.

, whose blood-borne precursors are not well defined, also differentiate in the tissues. They mainly reside near small blood vessels and, when activated, release substances that affect vascular permeability. Although best known for their role in orchestrating allergic responses, they are believed to play a part in protecting mucosal surfaces against pathogens.

The granulocytes are so called because they have densely staining granules in their cytoplasm; they are also sometimes called polymorphonuclear leukocytes because of their oddly shaped nuclei. There are three types of granulocyte, all of which are relatively short lived and are produced in increased numbers during immune responses, when they leave the blood to migrate to sites of infection or inflammation. , which are the third phagocytic cell of the , are the most numerous and most important cellular component of the innate : hereditary deficiencies in neutrophil function lead to overwhelming bacterial infection, which is fatal if untreated.  are thought to be important chiefly in defense against parasitic infections, because their numbers increase during a parasitic infection. The function of basophils is probably similar and complementary to that of eosinophils and mast cells; we shall discuss the functions of these cells in Chapter 9 and their role in allergic inflammation in Chapter 12. The cells of the myeloid lineage are shown in Fig. 1.4.

Figure 1.4 Myeloid cells in innate and adaptive immunity. Cells of the myeloid lineage perform various important functions in the immune response. The cells are shown schematically in the left column in the form in which they will be represented throughout the rest (more...)

The common lymphoid progenitor gives rise to the , with which most of this book will be concerned. There are two major types of lymphocyte: B lymphocytes or B cells, which when activated differentiate into plasma cells that secrete antibodies; and  or , of which there are two main classes. One class differentiates on activation into , which kill cells infected with viruses, whereas the second class of T cells differentiates into cells that activate other cells such as B cells and macrophages.

Most  are small, featureless cells with few cytoplasmic organelles and much of the nuclear chromatin inactive, as shown by its condensed state (Fig. 1.5). This appearance is typical of inactive cells and it is not surprising that, as recently as the early 1960s, textbooks could describe these cells, now the central focus of immunology, as having no known function. Indeed, these small lymphocytes have no functional activity until they encounter , which is necessary to trigger their proliferation and the differentiation of their specialized functional characteristics.

Figure 1.5 Lymphocytes are mostly small and in active cells. The left panel shows a light micrograph of a small lymphocyte surrounded by red blood cells. Note the condensed chromatin of the nucleus, indicating little trans-criptional activity, the relative absence (more...)

Lymphocytes are remarkable in being able to mount a specific  against virtually any foreign . This is possible because each individual lymphocyte matures bearing a unique variant of a prototype antigen receptor, so that the population of T and B  collectively bear a huge repertoire of receptors that are highly diverse in their antigen-binding sites. The  (BCR) is a membrane-bound form of the  that the  will secrete after activation and differentiation to plasma cells. Antibody molecules as a class are known as , usually shortened to , and the antigen receptor of B lymphocytes is therefore also known as  (). The  (TCR) is related to immunoglobulin but is quite distinct from it, as it is specially adapted to detect antigens derived from foreign proteins or pathogens that have entered into host cells. We shall describe the structures of these lymphocyte  in detail in Chapters 3, 4, and 5, and the way in which their diversity of binding sites is created as lymphocytes develop in Chapter 7.

A third lineage of lymphoid cells, called natural killer cells, lack antigen specific receptors and are part of the innate . These cells circulate in the blood as large  lymphocytes with distinctive cytotoxic granules (Fig. 1.6). They are able to recognize and kill some abnormal cells, for example some tumor cells and virus-infected cells, and are thought to be important in the innate immune defense against intracellular pathogens.

Figure 1.6 Natural killer (NK) cells. These are large granular lymphocyte-like cells with important functions in innate immunity. Although lacking antigen-specific receptors, they can detect and attack certain virus-infected cells. Photograph courtesy of N. Rooney (more...)

1-2. Lymphocytes mature in the bone marrow or the thymus

The lymphoid organs are organized tissues containing large numbers of  in a framework of nonlymphoid cells. In these organs, the interactions lymphocytes make with nonlymphoid cells are important either to lymphocyte development, to the initiation of adaptive immune responses, or to the sustenance of lymphocytes.  can be divided broadly into central or primary lymphoid organs, where lymphocytes are generated, and peripheral or secondary lymphoid organs, where adaptive immune responses are initiated and where lymphocytes are maintained. The central lymphoid organs are the  and the , a large organ in the upper chest; the location of the thymus, and of the other lymphoid organs, is shown schematically in Fig. 1.7.

 
Figure 1.7 The distribution of lymphoid tissues in the body. Lymphocytes arise from stem cells in bone marrow, and differentiate in the central lymphoid organs (yellow), B cells in bone marrow and T cells in the thymus. They migrate from these tissues and are carried (more...)

Both B and  originate in the  but only B lymphocytes mature there; T lymphocytes migrate to the  to undergo their maturation. Thus B lymphocytes are so-called because they are bone marrow derived, and T lymphocytes because they are thymus derived. Once they have completed their maturation, both types of lymphocyte enter the bloodstream, from which they migrate to the peripheral lymphoid organs.

1-3. The peripheral lymphoid organs are specialized to trap antigen, to allow the initiation of adaptive immune responses, and to provide signals that sustain recirculating lymphocytes

Pathogens can enter the body by many routes and set up an infection anywhere, but  and  will eventually encounter each other in the peripheral lymphoid organs—the lymph nodes, the , and the mucosal lymphoid tissues (see Fig. 1.7). Lymphocytes are continually recirculating through these tissues, to which antigen is also carried from sites of infection, primarily within macrophages and dendritic cells. Within the lymphoid organs, specialized cells such as mature dendritic cells display the antigen to lymphocytes.

The lymph nodes are highly organized lymphoid structures located at the points of convergence of vessels of the , an extensive system of vessels that collects extracellular fluid from the tissues and returns it to the blood. This extracellular fluid is produced continuously by filtration from the blood, and is called lymph. The vessels are lymphatic vessels or lymphatics (see Fig. 1.7).  drain fluid from the tissues and also carry -bearing cells and antigens from infected tissues to the lymph nodes, where they are trapped. In the lymph nodes, B  are localized in , with  more diffusely distributed in surrounding paracortical areas, also referred to as . Some of the B-cell follicles include germinal centers, where B cells are undergoing intense proliferation after encountering their specific antigen and their cooperating T cells (Fig. 1.8). B and  are segregated in a similar fashion in the other peripheral lymphoid tissues, and we shall see that this organization promotes the crucial interactions that occur between B and T cells upon encountering antigen.

  Figure 1.8 Organization of a lymph node. As shown in the diagram on the left, a lymph node consists of an outermost cortex and an inner medulla.
The cortex is composed of an outer cortex of B cells organized into lymphoid follicles, and deep, or aracortical, areas (more...)

The  is a fist-sized organ just behind the stomach (see Fig. 1.7) that collects  from the blood. It also collects and disposes of senescent red blood cells. Its organization is shown schematically in Fig. 1.9. The bulk of the spleen is composed of , which is the site of red blood cell disposal. The  surround the arterioles entering the organ, forming areas of , the inner region of which is divided into a  (PALS), containing mainly , and a flanking .

Figure 1.9  Organization of the lymphoid tissues of the spleen. The schematic at top right shows that the spleen consists of red pulp (pink areas in the top panel),
which is a site of red blood cell destruction, interspersed with lymphoid white pulp. An enlargement of (more...)     
 

The  (), which include the ,  , and , and specialized structures called Peyer's patches in the small intestine, collect  from the epithelial surfaces of the gastrointestinal tract. In Peyer's patches, which are the most important and highly organized of these tissues, the antigen is collected by specialized epithelial cells called multi-fenestrated or . The  form a follicle consisting of a large central dome of B lymphocytes surrounded by smaller numbers of  (Fig. 1.10). Similar but more diffuse aggregates of lymphocytes protect the respiratory epithelium, where they are known as bronchial-associated lymphoid tissue (), and other mucosa, where they are known simply as  (). Collectively, the mucosal  is estimated to contain as many lymphocytes as all the rest of the body, and they form a specialized set of cells obeying somewhat different rules.

Figure 1.10 Organization of typical gut-associated lymphoid tissue. As the diagram on the left shows, the bulk of the tissue is B cells, organized
in a large and highly active domed follicle. T cells occupy the areas between follicles. The antigen enters across a specialized  (more...)

Although very different in appearance, the lymph nodes, , and mucosal-associated lymphoid tissues all share the same basic architecture. Each of these tissues operates on the same principle, trapping  from sites of infection and presenting it to migratory small , thus inducing adaptive immune responses. The peripheral lymphoid tissues also provide sustaining signals to the lymphocytes that do not encounter their specific antigen, so that they continue to survive and recirculate until they encounter their specific antigen. This is important in maintaining the correct numbers of circulating T and B lymphocytes, and ensures that only those lymphocytes with the potential to respond to foreign antigen are sustained.

1-4. Lymphocytes circulate between blood and lymph

Small B and  that have matured in the  and  but have not yet encountered  are referred to as naive lymphocytes. These cells circulate continually from the blood into the peripheral lymphoid tissues, which they enter by squeezing between the cells of capillary walls. They are then returned to the blood via the lymphatic vessels (Fig. 1.11) or, in the case of the , return directly to the blood. In the event of an infection, lymphocytes that recognize the infectious agent are arrested in the lymphoid tissue, where they proliferate and differentiate into effector cells capable of combating the infection.

Figure 1.11 Circulating lymphocytes encounter antigen in peripheral lymphoid organs. Naive lymphocytes recirculate constantly through peripheral lymphoid tissue, here illustrated as a lymph node behind the knee, a popliteal lymph node. Here, they may encounter their (more...)

When an infection occurs in the periphery, for example, large amounts of  are taken up by dendritic cells which then travel from the site of infection through the afferent lymphatic vessels into the draining lymph nodes (see Fig. 1.11). In the lymph nodes, these cells display the antigen to recirculating , which they also help to activate. B cells that encounter antigen as they migrate through the lymph node are also arrested and activated, with the help of some of the activated . Once the antigen-specific lymphocytes have undergone a period of proliferation and differentiation, they leave the lymph nodes as effector cells through the  (see Fig. 1.8).

Because they are involved in initiating adaptive immune responses, the peripheral lymphoid tissues are not static structures but vary quite dramatically depending upon whether or not infection is present. The diffuse mucosal lymphoid tissues may appear in response to infection and then disappear, whereas the architecture of the organized tissues changes in a more defined way during an infection. For example, the B-cell  of the lymph nodes expand as B  proliferate to form germinal centers (see Fig. 1.8), and the entire lymph node enlarges, a phenomenon familiarly known as swollen glands.

Summary

Immune responses are mediated by leukocytes, which are derived from precursors in the . A pluripotent hematopoietic stem cell gives rise to the  responsible for adaptive immunity, and also to myeloid lineages that participate in both innate and adaptive immunity. , eosinophils, and basophils are collectively known as granulocytes; they circulate in the blood unless recruited to act as effector cells at sites of infection and inflammation.  and mast cells complete their differentiation in the tissues where they act as effector cells in the front line of host defense and initiate inflammation. Macrophages phagocytose , and recruit other phagocytic cells, the neutrophils, from the blood.  are exocytic and are thought to orchestrate the defense against parasites as well as triggering allergic inflammation; they recruit eosinophils and basophils, which are also exocytic.  enter the tissues as immature phagocytes where they specialize in ingesting antigens. These -presenting cells subsequently migrate into lymphoid tissue. There are two major types of lymphocyte: B lymphocytes, which mature in the bone marrow; and , which mature in the . The bone marrow and thymus are thus known as the central or primary lymphoid organs. Mature lymphocytes recirculate continually from the bloodstream through the peripheral or secondary lymphoid organs, returning to the bloodstream through the lymphatic vessels. Most adaptive immune responses are triggered when a recirculating T cell recognizes its specific antigen on the surface of a dendritic cell. The three major types of peripheral lymphoid tissue are the , which collects antigens from the blood; the lymph nodes, which collect antigen from sites of infection in the tissues; and the mucosal-associated lymphoid tissues (), which collect antigens from the epithelial surfaces of the body. Adaptive immune responses are initiated in these peripheral lymphoid tissues:  that encounter antigen proliferate and differentiate into antigen-specific effector cells, while B cells proliferate and differentiate into -secreting cells.

References

Janeway Charles A, Paul Travers, Mark Walport, and Mark J Shlomchik, Immunobiology, 5th edition The Immune System in Health and Disease, New York: Garland Science; 2001.  Janeway: Book Immune system in health & disease 2001

Copyright © 2001, Garland Science.