Section I. IMMUNOGENETICS
a. Immunogenetics is the study of processes involved in the immune response
that may have a genetic basis. These processes include all the factors that control the
immune response of the host, as well as the transmission of antigenic specificities from
generation to generation.
b. The field of immunogenetics can be divided into two broad areas of study.
(1) The first major area concerns the genetic regulation and control of the
immune system itself. The maturation of the immune cells in a given individual is an
example of genetic control of cellular proliferation and differentiation. Interruption or
alterations of these developmental sequences lead to immunodeficiency disorders,
autoimmune disorders, and perhaps malignancies, as the cells escape the influence of
their normal control mechanisms.
(2) The second area with the broadest application is the use of antibodies
and sensitized immune cells, the products of the immune system, as probes to detect
and characterize various antigens that may show genetic variation.
c. The major histocompatibility complex (MHC) is the region of a specific
chromosome that controls histocompatibility. This is related in concept to concerns that
donated tissues or organs not be rejected by their host, that is, be compatible. The term
histocompatibility refers to the presence of certain antigens which mean that the host
of an organ or tissue graft will not reject the graft. In humans, the MHC is called the
HLA complex, which refers to "human leukocyte antigens." Histocompatibility is a
relationship of donor and host based upon the presence of compatible HLA antigens.
GENETICS OF IMMUNE REGULATION
Several early observations had suggested a genetic basis for the immune
response. Studies on human immune response (Ir) genes had been stimulated by the
recognition of the overall homology of the HLA complex with major histocompatibility
complexes of animals. A large number of genes exist that code for the regulatory
components of the complex network of the immune system. It was originally thought
that the genes controlling the immune response were located within the genetic
segment coding for histocompatibility antigens. Although the histocompatibility-linked Ir