Basic Immunology

This page is provided for educational purposes.*

In short, immune function consists of:Basic Immunology

  • Preventing entry
  • Detection / identification
  • Neutralizing
  • Destruction
  • Engulfing
  • Removal of antigens (anything foreign or abnormal which could be a splinter or cancer cell and pathogens such as bacteria, virus, and parasites).

Methods of immune function can be described in two basic parts, each with several modes of action.

  1. Non-specific (innate) immunity occurs quickly and provides consistent and effective protection for the majority of pathogens. It consists of:
      1. Barriers to entry such as skin, body fluids, low pH of stomach, ciliary action of lungs, mucous linings of lungs and GI tract
      2. Several types of Phagocytes (neutrophils, monocytes, macrophages, dendritic cells, and mast cells) that engulf (eat) non- self then kill by several methods:
        • Disinfection by hydrogen peroxide or hypochlorite
        • Spearing the membrane electrically
        • Breaking the cell wall with enzymes
        • Starving them of iron

    Phagocytes can also poison pathogens without eating them.

    1. Natural Killer cells effectively spear non- self cells like a magic bullet. They are important for destruction of pathogens.

    Note: Non-specific immune function is also important to specific immunity. Phagocytes pick up foreign cells poisoned by lymphotoxins and those identified by antibodies. Macrophages and dendritic cells present (show) antigens to plasma cells directing specific antibody production.

    When pathogens escape the non-specific defense mechanisms, specific immunity will be directed against them.

  2. The Specific (Adaptive or Acquired) immune responses.
    1. The first response of the adaptive immune system is called cell mediated. Lymphocytes are quickly turned into Killer T cells (T cells because they are regulated by the thymus). They produce substances like lymphotoxins that poison or lyse (blow up) the invader.
    2. Regulatory T suppressor cells (Ts) know when and how to shut down the killer T’s to avoid collateral damage. T helper cells (Th) help activate the 2nd response of adaptive immunity by telling B lymphocytes (think bone marrow) to produce antibody through the creation of plasma cells.
    3. The creation of antibody takes several days largely because it takes time to locate the antigen prior to creating the antibody. It is a highly specific and potent response and because of immunologic memory for both T and B cells, the second response to the same antigen is much faster and more effective than the first. This is why vaccinations are important and effective. They are used as a preventative of diseases rather than a treatment.

    Classes of Antibody or Immunoglobulin (Ig)

    • IgG antibody accounts for the vast majority of all antibody mediated protection even though it is the slowest to be produced after the initial insult. Its primary means of protection is to identify the pathogen by attaching to it and marking it for destruction by other immune cells. It can also burst cells by fixing complement. Complement is a group of proteins that build on one another after the initial component has been “fixed”, much like the first domino must be tipped over to topple the whole row. Once the “row” has been completed, the complement has the ability to pierce the cell wall of the antigen. Typically only gram negative bacteria can be pierced (lysed) by a particular chain of complement known as the membrane attack (MAC). Gram positives can fall prey to the complement cascade but through the identification route.
    • IgA protects the mucosal surfaces (gut, respiratory and urogenital tract). It is similar to IgG in that it has the ability to identify and mark a pathogen for destruction by other immune cells such as phagocytes. It also has the ability to fix complement although the complement cascade is slightly different than IgG and IgM.
    • IgM is a first response antibody, offering protection from pathogens much faster than IgG upon first exposure to antigen. Like IgG it can trigger what is called the complement cascade, but is much more efficient at doing so.
    • IgE can perform the same functions as described for IgG and is effective against parasites. However it is often best known for its part in allergic reactions.
    • IgD is not as well described as the other 4 classes. It probably has a role in the activation of B cells to produce IgG by being a receptor for a broad range of antigens.

    Note: IgE and IgD are not found in any appreciable amount in colostrum.

    Antibodies perform their mission in several ways:

    • Agglutinins cause the clumping together of bacterial cells (agglutination). This reaction has been used as a visual test for Bang’s disease (sometimes called contagious abortion or undulant fever in man, Brucellosis) in cattle for many decades.
    • Bacteriolysins cause bacterial cells to dissolve or liquefy (lysis). A network of proteins known as complement assists this particular mechanism. IgG, IgA and IgE are capable of fixing complement.
    • Opsonins coat the bacteria identifying them for phagocytes.
    • Antitoxins neutralize toxins. An application of this is antiserum for snake bites.
    • Precipitins cause antigens to precipitate in a liquid media.
    *These statements have not been evaluated by the Food and Drug Administration. Colostrum is not intended to diagnose, treat, cure or prevent any disease.