1. Foreign antigens (molecules) elicit an immune response from a host.
2. Antibodies and cytokines produced by the immune system attack foreign antigens.
3. As many as 20,000 genes in the human genome may be, directly or indirectly, involved in an immune response.
2. 1. Foreign antigens (molecules) elicit an immune response from
a host.
2. Antibodies and cytokines produced by the immune system
attack foreign antigens.
3. As many as 20,000 genes in the human genome may be,
directly or indirectly, involved in an immune response.
The Importance of Cell Surfaces
3. 1. Results of early transfusions were inconsistent.
2. With the discovery of human blood groups systems, properly matched
donor and recipient types resulted in successful transfusions.
3. Blood types, including the ABO groups, Rh factor, and others, result
from self antigen patterns on red blood cells.
4. Rh incompatibility may put a fetus at risk.
5. RhoGAM can be used to prevent Rh incompatibility.
Blood Groups
4. The Human Leukocyte Antigens
1. In addition to blood group antigens, a large number of cell surface molecules are
recognized by the immune system.
2. Many of the cell surface proteins that help to establish immunity are encoded by the
approximately seventy genes of the major histocompatibility complex (MHC) located on
chromosome 6 in humans.
3. Class I and II genes of the MHC encode human leukocyte antigens (HLA).
4. Class III genes produce plasma proteins involved in the immune response.
HLA is the human version of the major histocompatibility complex (MHC), a gene
family that occurs in many species. In humans, the MHC complex consists of more
than 200 genes located close together on chromosome 6. Genes in this complex are
categorized into three basic groups: class I, class II, and class III.
5. 5. HLA antigens on leukocytes are involved in processing of foreign antigens.
6. HLA proteins are each encoded by several genes with many alleles and as
a result only 2 in every 20,000 unrelated people match for the six major HLA
genes by chance.
7. Individuals with certain HLA combinations have an increased risk of
developing certain HLA-linked diseases.
6. HLA genes have many possible variations, allowing each person's immune system to
react to a wide range of foreign invaders. Some HLA genes have hundreds of identified
versions (alleles), each of which is given a particular number (such as HLA-B27). Closely
related alleles are categorized together; for example, at least 40 very similar alleles are
subtypes of HLA-B27. These subtypes are designated as HLA-B*2701 to HLA-B*2743.
More than 100 diseases have been associated with different alleles of HLA genes. For
example, the HLA-B27 allele increases the risk of developing an inflammatory joint
disease called ankylosing spondylitis. Many other disorders involving abnormal immune
function and some forms of cancer have also been associated with specific HLA alleles
However, it is often unclear what role HLA genes play in the risk of developing these
diseases .
7. 1. At the cellular level the immune system consists of
various types of lymphocytes and macrophages.
2. The immune response consists of an immediate,
generalized, innate immunity and a slower, more specific
adaptive immunity.
The Immune System
8. 1. Skin, mucous membranes, tears, and saliva are examples of physical
and chemical barriers that keep pathogens from entering the body.
2. Pathogens that breach this barrier encounter an innate immune
response consisting of inflammation, phagocytosis, complement,
collectins, and cytokines.
Physical Barriers and the Innate Immune Response
9. 1. The innate response is rapid (minutes) while the aquired immune
response must be stimulated to action and takes days to respond.
2. The acquired immune response is divided into the humoral and cellular
immune responses. Both of these responses differ from the innate immune
response in that they are more complex, highly specific and each has a
cellular component with memory.
3. The humoral response involves B cells that secrete antibodies in order to
neutralize, clump, and stimulate the destruction of pathogens by recognizing
and binding specific foreign antigens.
The Adaptive (Acquired) Immune Response
10. 4. Antibodies are made of Y-shaped polypeptides consisting of constant
and variable regions.
5. The astounding diversity of antibody binding activities is due to a
shuffling of gene pieces (exons) encoding antibody polypeptide products in
B cells.
6. In the cellular immune response, helper T cells stimulate B cells to
manufacture antibodies and cytotoxic T cells to secrete cytokines.
7. Some T cells bind to nonself cells and virus-covered cells and burst
them. Other T cells function to coordinate the immune response.
