Genetics of Immunity Part 2 Major Histocompatibility Complex

Genetics of Immunity: Part 2

Major Histocompatibility Complex ● MHC, a region that includes about 70 genes located on the short arm of chromosome 6 ● MHC genes encode the Human Leukocyte Antigens (HLAs) -- first studied white blood cells Karyotype- photograph of human chromosomes, arranged in pairs

Human Leukocyte Antigens (HLAs) ● A person’s HLA “type” identifies all of his or her cells as “self, ” or belonging to the same individual → HLA Markers ● An individual’s overall HLA type is based on 6 major genes ○ Vary genetically -- only 2 / 20, 000 unrelated people match for the six genes by chance ○ Doctors match people for transplants by determining how alike the individuals are for these 6 genes ■ Usually 4/6 genes must match for a chance at successful transplantation

Antigen Presenting Cell A macrophage (large, phagocytic cell) engulfs a bacterium & displays foreign bacterial antigens on macrophage surface → alerts other immune system cells ● Helper T cells recognize antigens & bind to macrophage → start series of immune events

Human Immune System Network of vessels (lymphatics) that transport lymph fluid to bean shaped structures around the body called _______ - The spleen and thymus gland Also make up the immune system Lymph fluid carries white blood cells (_________) specifically called lymphocytes. There are two major types of lymphocytes → B cells and T cells

B Cells & T Cells Both made in the bone marrow: ● B-cells mature in the bone marrow while T-cells travel through the bloodstream and mature at thymus gland 1) B-cells fight bacteria/viruses by making Y-shaped antibodies 2) T-cells: initiate cell mediated immunity (without need of antibiotics but rather with the use of white blood cells)

B Cells After T cell finds a B cell match, it releases cytokines (cell signaling proteins) that stimulate the B cell to divide into 2 types: 1) Plasma Cells- antibody factories each secreting up to 2, 000 antibodies/sec 2) Memory B Cells- fewer and usually dormant; respond to foreign pathogens faster on the secondary immune response https: //www. youtube. com/watch? v=Jn. Xx. U 5 XAVWU

T Cells Three Types of T Cells: 1) Helper T-cells stimulate B-cells to make antibodies and help killer cells develop. 2) Killer/Cytotoxic T-cells directly kill cells that have already been infected by a foreign invader 3) Regulatory T-cells suppress immune response when no longer needed

Antibody Structure A Y-shaped sub unit that includes: -Four Polypeptide Chains (2 heavy, 2 light joined by disulfide bond) with: -Constant Regions- lower portion of each chain is a relatively generic amino acid sequence -Variable Regions- upper portions have greater variability that help provide the specificity of antibodies to antigens -Antigen Binding Sites- specialized ends of variable regions

Immune Response ● Attacks pathogens, cancer cells, and transplanted cells with two lines of defense 1) Immediate, generalized innate immune response 1) More specific, slower adaptive (acquired) immune response

Innate Immunity Innate- existing in one from birth; native -refers to basic resistance to disease that an individual is born with 1) Provides the first line of defense against invading pathogens until an adaptive immune response develops 2) present at all times 3) does not increase w/ repeated exposure Examples: physiological barriers, inflammation, phagocytosis

Acquired/Adaptive Immunity obtained from the development of antibodies in response to exposure to an antigen (vaccination) or an attack of an infectious disease -From the transmission of antibodies from mother to fetus through the placenta -Includes development of immunological memory, begins after 12 hrs of an infection being present Examples: chickenpox vaccine, polio vaccine, exposure to mononucleosis

Cytokines play a role in both innate and adaptive immunity ● Interferons are cytokines that alert other parts of immune system of presence of infected cells ● Interleukins are cytokines that cause fever, temporarily increasing body temperature that kills some bacteria and viruses ● Tumor Necrosis Factors are cytokines that destroy bacterial toxins and attack cancer cells

Immune Responses Humoral Immune Response- B cells produce antibodies after activation by T cells Cellular Immune Response- T cells produce cytokines and activate other cells Primary Immune Response- the response initiated after the first assault by a foreign pathogen Secondary Immune Response- the second assault → activates immune system “memory” some infections like chicken pox, once ex) why we only get