Anatomy & Physiology II Unit Ten

Body Defenses The immune system protects the body from invasion by pathogens (infectious microbes, toxins & radiation) The human immune system is comprised of two types of defenses: > nonspecific > specific

Nonspecific Body Defenses Nonspecific defenses are those that react the same no matter the pathogen that is attempting to invade the body These nonspecific defenses are the first line of defense against invasion

Nonspecific Body Defenses The five types of nonspecific defenses: > barriers > phagocytes > fever > interferons > inflammatory response

Nonspecific Body Defenses Barriers such as the skin and mucous membranes prevent pathogens from gaining access to the body These barriers also secrete a number of enzymes that can destroy or inhibit the growth of microbes

Nonspecific Body Defenses Phagocytes are the different types of WBCs and macrophages that are found in the lymphatic system, blood and body tissues that consume any pathogens or foreign materials

Nonspecific Body Defenses Fever (pyrexia) is the elevation of body temperature so as to cause the liver & spleen to hoard zinc & iron, depriving bacteria of minerals needed to reproduce Temperature elevation is due to the release of interleukin by active neutrophils and macrophages

Nonspecific Body Defenses Interferons are proteins secreted by cells that have been infected by viruses These proteins alert surrounding cells so they can prevent infection and activate macrophages to destroy already infected cells

Nonspecific Body Defenses The inflammatory response is a localized reaction to injury, trauma or infection Its primary functions are: > contain the spread of pathogens and destroy them > clean up tissue damage & debris > promote tissue repair

Nonspecific Body Defenses

Specific Body Defenses Specific defenses involve immunity which can be cellular or humoral and memory Immunity is directed against a specific pathogen and the memory component recognizes the pathogen if it is reintroduced

Specific Body Defenses Lymphocytes are the backbone of immunity and there are two types - T lymphocytes & B lymphocytes T lymphocytes (T cells) are active in cellular immunity, attacking pathogens and infected cells directly

Specific Body Defenses B lymphocytes (B cells) are active in humoral immunity, using antibodies to render pathogens inactive or by clumping the pathogens so they are not active and phagocytes will then consume them

Specific Body Defenses

Specific Body Defenses

Primary Immune Response Secondary Immune Response Specific Body Defenses Primary Immune Response Secondary Immune Response

Specific Body Defenses Active humoral immunity occurs when B cells encounter antigens and begin producing antibodies This immunity can be acquired by infection or vaccination and is very powerful in that it invokes the secondary immune response

Specific Body Defenses Passive humoral immunity occurs when antibodies are transferred to the blood Antibodies are transferred from mother to fetus or artificially through injections B cells are not activated so immunity is temporary

Specific Body Defenses Immunoglobulin (antibodies) are produced by B cells during humoral response There are five major classes of immunoglobulins based on the location of their protein chains

Specific Body Defenses Immunoglobulin classes: •IgM – pentamer in shape •IgA – dimer in shape •IgD – monomer in shape •IgG – monomer in shape •IgE – monomer in shape

Infectious Agents Bacteria cause stress (sickness) by producing toxins that may damage or destroy cells Bacterial infections are treated postsymptomaticaly with antibiotics

Infectious Agents Viruses cause stress (sickness) by injecting their nucleic acid into a cell, which will then use the resources of the cell to replicate more viruses After filling with new viruses, the cell will lyse and be destroyed

Infectious Agents Viral diseases are treated presymptomaticaly with vaccines Once a viral infection has occurred, the symptoms must run their course

Infectious Agents Human immunodeficiency virus (HIV) infects and destroys helper T cells Without helper T cells the entire immune response shuts down, rendering the individual defenseless against infection