Chapter 17: Genetics of Immunity Section 17.1: Importance of Cell Surfaces Section 17.2: Human Immune System

Why are cell surfaces important? Cells need to recognize each other so foreign bodies can be identified and destroyed. Autoimmune disease (ex: rheumatoid arthritis, lupus) are diseases in which the body attacks itself because it can’t recognize it’s cells. If cells can’t recognize viruses/bacteria to destroy them then the cells will be under attack.

How is immunity controlled by your genes? Genes that affect immunity may make you susceptible or resistant to certain diseases May make you more prone to autoimmune diseases or allergic reactions. Symptoms may vary depending on how many of these genes are inherited. Genes that control the making of antibodies, cytokines, or antigens can affect immunity.

Types of Autoimmune disorders These are autoimmune type disorders in which the body attacks itself. – Rheumatoid arthritis- joints – Multiple sclerosis- brain & spinal cord – Systemic lupus- heart, brain,kidneys attacked – Psoriasis- skin attacked – Grave’s disease- thyroid

Cell Surface Proteins: Blood Type Antigens RBC have antigens attached to outside of cell – Type A has A antigens & produces anti-B antibodies – Type B has B antigens & produces anti-A antibodies – Type AB has A & B antigens & produces no antibodies – Type O has neither A or B antigens If incorrect blood is “transplanted”, clumping will occur leading to death.

Blood type compatibility DonorRecipient OO, A, B, AB AA, AB BB, AB AB

Cell Surface Proteins: Rh Factors Rh stands for rhesus monkeys which were the animals in which these factors were 1 st identified. If you are Rh+ then your RBC has an RhD antigen on the outside of it. If Rh- woman has Rh+ baby her body will produce antibodies against the Rh+ antigens. In this 1 st pregnancy, antibody population is low so fetus not affected. In second pregnancy, the woman’s body has a chance to build antibodies which will attack 2 nd fetus. Fetus will experience circulatory problems and organ failure. Mother must get RhoGAM shot during and after pregnancy to counteract the Rh antibodies.

Cell Surface Proteins: Human Leukocyte Antigens (HLAs) There are 6 genes that code for HLAs When an organ transplant is being considered between two people, HLA compatibility must be considered to make sure the person’s body does not reject or attack new donated organ. Four out of 6 should match to have a chance for success.

Cell Surface Proteins: Human Leukocyte Antigens (HLAs) Controlled by the Major Histocompatability Complex (MHC) on short arm of chromosome 6 Link to sugars and make long chains outside cell. Trap virus/bacteria, tagging it for destruction by other WBCs. Type 1 & 2 differ in the types of immune cells they alert.

What are antigen-presenting cells? When invader is engulfed by a type of WBC called a macrophage, the macro will dismantle the invader and add the invader’s antigens to their own proteins outside the cell. Helper T cells recognize this protein configuration, bind to macrophage, initiate immune response.

The Human Immune Response Three levels of immune protection – Physical Barriers – Innate Immunity – Adaptive Immunity

Physical Barriers Unbroken skin is largest defense Mucous membranes – Ears, nose, mouth, lungs – Trap invaders Stomach acids – Kill most microbes Diarrhea, tears, urination – Body recognizes invader and tries to flush out quickly.

Innate Immunity If pathogen breaches physical barriers, innate immunity activated Defense system already in place so ready for pathogen battle. Causes inflammation reaction to create a hostile environment for pathogen.

Inflammation reaction WBCs are activated to phagocytize (engulf) invaders. – Neutrophils – Macrophages – Natural Killer Cells Plasma accumulates to dilute toxins bring in antimicrobial chemicals. Histamine released from mast cells causes blood vessels to dilate, increases blood flow. Area turns red and swelling occurs. More WBCs leave blood vessel through gaps and go to affected tissue. Interleukin cytokine cells cause fever which tries to make area too hot for invader to survive.

Adaptive Immunity Must be stimulated Can take days to respond. Very specific Two types: – Humoral Immune Response – Cellular Immune Response

Humoral Immune Response B cells produce antibodies that go to other locations and cause immune reaction. Antigen presenting macrophage activates a T cell T cell stimulates B cells – B cells have surface protein that attaches to foreign antigens B cells are stimulated to divide and become one of two types – Plasma cells- antibody factories to immediately fight infection (primary immune response) – Memory cells- fewer, dormant cells that respond if invader appears again. (secondary immune response)

Cellular Immune Response T cells travel to infection site to fight. T cells leave bone marrow and travel to thymus gland where they mature & differentiate Types: – Helper T – Cytotoxic T cell (killer T)

1. Helper T cells Functions: – Recognize foreign antigens on macrophages – Stimulate B cells to make antibodies – Secrete cytokines Interleukins Interferons Tumor necrosis factor Colony stimulating factors All interact and signal each other – Activate cytotoxic (killer) T cells – Slow down immune response as infection clears Types: – Varies based on surface antigens – Ex: CD4 helper T cells attacked by HIV b/c HIV recognizes the CD4 antigens on T cell surface

2. Cytotoxic (killer) T cells CD8 receptors on surface Attack cells infected with virus or cancer Cytotoxic T cell binds to cancer cell, injects perforin (protein) that pierces cancer cell membrane and pops it. Macrophages clean up cancer cell pieces.