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KEY CONCEPTS

KEY CONCEPTS

  • image Cells of the immune system are derived from the pluripotent stem cell. Hematopoiesis is closely regulated to assure adequate numbers of different cell types. The development of these different cells or cell lineages depends on cell-to-cell interactions and hematopoietic growth factors.

  • image Upon activation, dendritic cells (DCs) express higher concentrations of major histocompatibility complex class II molecules, B7-1, B7-2, CD40, ICAM-1, and LFA-3 molecules than other antigen-presenting cells (APCs). They also produce more IL-12. These differences may explain why, in vitro, DCs are the most efficient APC.

  • image A T lymphocyte expresses hundreds of T-cell receptors (TCRs). All the TCRs expressed on the surface of an individual T lymphocyte have the same antigen specificity.

  • image An immature B lymphocyte expresses thousands of membrane-bound surface immunoglobulin (sIg) as IgM (monomeric) or IgD, all with the same specificity (ie, antigen-binding site). Upon antigen stimulation and T cell help, the immature B lymphocyte matures (proliferates, class-switches and becomes a plasma cell) to secrete different isotypes (eg, IgM [pentamer], IgA, immunoglobulin G [IgG], and IgE) with the same specificity as the original membrane-bound sIg.

  • image Serum protein electrophoresis determines the total concentration of all circulating proteins, including the immunoglobulins (ie, IgG, IgA, IgM, IgD, and IgE). The concentration of the individual isotypes can be determined with isotype-specific quantification methods. Most clinical laboratories quantitate only IgG, IgM, and IgA because they are the most prevalent isotypes in the bloodstream. In patients with allergic disorders, quantification of IgE is rarely useful.

  • image An understanding of the mechanism of action of immunomodulators allows a clinician to anticipate potential adverse effects. The benefit of manipulating immune responses must be balanced with the potential consequences and long-term sequela (eg, tumor growth, infections, etc) of such manipulation.

The immune system is a complex network of barriers, organs, cellular elements, and molecules that interact to defend the body against invading pathogens. The immune system is actually composed of two distinct systems of immunity: innate immunity and adaptive immunity. In brief, innate immunity includes a series of nonspecific barriers (physical and chemical), along with cellular and molecular elements strategically deployed and positioned to prevent or quickly neutralize infection. Adaptive immunity works in concert with the innate immune system. In contrast to innate immunity, adaptive immunity constantly evolves and adapts to the invading pathogens. The hallmarks of the adaptive immune response are; diversity, memory, mobility, self-versus nonself-discrimination, redundancy, replication, and specificity.1 Diversity indicates the capability of the immune system to respond to many different pathogens or strains of pathogens. Immunological memory ensures a quicker and more vigorous response to a subsequent encounter with the same pathogen. If an individual has seen something before, the odds are good that he or she will see it again. So the individual will make more of these cells and have them ready. Mobility of components of the immune system enables local reactions to provide systemic protection. Discrimination of self ...

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