Immunity

Primary Function of the Immune System n Provides protection against disruption by pathogens or toxins n Helps discriminate between “self” and “nonself” Pathogen - Definition: –Any disease causing agent (microorganisms) Types: –Bacteria –Viruses –Parasites –Fungi

Pathogen Comparison Bacteria vs. Virus n Yes n Enters body, makes proteins & enzymes that are toxic (antigens) n?n? –Not a cell –DNA+ protein n Not without a host n No, can only treat symptoms –1)injects DNA into host –2)Uses host’s machinery to make more viruses –3)host breaks open releasing virus copies n Are they living? n Can they reproduce? n Do antibiotics work? n How do they attack?

The Defenses Non-Specific Definition: –Agents do not have to recognize a foreign invader to fight it (work by preventing pathogen from entering the body) Examples: –Skin –Tears –Saliva –Sweat –Mucus –Macrophage

The Defenses Specific Definition: –Agents attacks only certain invaders, specialized defense Types of Cells –Helper T cells 1st line of specific defense Help recruit other immune cells & tell them to attack certain invaders –Killer T cells Can distinguish virus infected cells from uninfected cells by the unique molecular signals on the infected cells surface –B cells Told by helper T cells to make antibodies to prevent specific antigens from hurting the body…. “Memory”

Lymphocyte Function T cell response –Attach to foreign antigen bearing cells and interact directly Cell Mediated Immunity Antibody Mediated Immunity B cell response –Differentiate into plasma cells –Produce antibodies

Antibodies & Antigens Proteins Can recognize chemical signals from another cell (pathogen) “Self” Y shape Chemical signal on the surface of a pathogen

Cell Mediated Immunity Killer (cytotoxic) T cells Killer T cells recognize body cells infected with a virus; then destroy those cells by drilling holes in their plasma membranes.

Cell or Antibody Mediated Immunity Helper T cells Helper T cells start the immune response by activating B or T cells.

Macrophage Antigen-presenting cell Helper T cell Antigen-presenting cell APC B cell suppressor T cell cytotoxic T cell T cells and cell-mediated immunity

Antibody Mediated Immunity B cells –Activated when it encounters an antigen that fits its antigen receptor –Proliferates (colonial expansion) Plasma cells-- >antibodies Memory cells-->future fights

Vaccines n What is in the shot they give you? –Dead or inactive (attenuated) pathogens n How does it work? –Cause B cells to make antibodies against the foreign antigen

The Memory of Infection

Autoimmune Disorders n “Auto” = self n Definition: a disease in which the immune system attacks the tissue of the body; cause is generally unknown n Immune system distinguishes “self” from “non-self n Examples: –multiple sclerosis (MS) - T cells destroy myelin sheath around neurons

Cold Virus, Rubella, & Strep n Common Cold Virus –Influenza ; contagious viral infection of the nose, throat and lungs which often occurs in the winter. n Rubella virus –German measles n Streptococcus bacterium –Strep throat is an infection of the pharynx caused by streptococcus bacteria. Treatments: –Strep Throat Antibiotics such as penicillin or erythromycin –Rubella Vaccine –Influenza