Chapter 17 Specific Defenses of the Host - Immune Response

Vocabulary flashcards covering key terms and concepts from the lecture notes on the immune response.

Specific Defenses

Specific resistance, the third line of defense, effective against particular pathogens.

Immunity

Involves a specific defensive response to an invasion by foreign organisms or foreign substances.

Antigens

Organisms or substances that provoke an immune response.

Acquired Immunity

The protection an animal develops against certain types of microbes or foreign substances over the lifetime of the individual.

Naturally Acquired Active Immunity

Obtained when exposed to antigens in the course of daily life.

Naturally Acquired Passive Immunity

Involves the natural transfer of antibodies from a mother to her infant (transplacental transfer or colostrum).

Artificially Acquired Active Immunity

Results from vaccination, introducing specially prepared antigens called vaccines into the body.

Artificially Acquired Passive Immunity

From the introduction of antibodies into the body from an animal or person who is immune.

Humoral (antibody-mediated) Immune System

Involves the production of antibodies against foreign organisms or substances found in extracellular fluids. B cells produce antibodies.

Cell-Mediated Immune System

Involves special lymphocytes called T cells that act against foreign organisms or tissues. Effective against intracellular pathogens, fungi, protozoa, and helminths.

Antigens

Mostly proteins or large polysaccharides, foreign to the body, and often components of invading microbes. Antibodies recognize specific regions called antigenic determinants or epitopes.

Antibodies

Proteins made in response to an antigen that can recognize and bind to that antigen. Members of the group of soluble proteins known as immunoglobulins (Igs).

Immunoglobulin Classes

IgG, IgM, IgA, IgD, and IgE.

IgG Antibodies

Monomer, 80% of serum Abs, fix complement, cross blood vessel walls and placenta, protect against circulating bacteria and viruses, neutralize bacterial toxins.

IgM

5-10% of antibodies in serum, pentamer structure, remains in blood vessels, predominant antibody type in response to ABO blood group antigens, first antibodies to appear after antigen exposure.

IgA

10-15% of antibodies in serum, most abundant in mucous membranes and body secretions, prevents attachment of pathogens to mucosal surfaces.

IgD

Only 0.2% of total serum antibodies, found in blood, lymph, and on the surface of B cells, act as antigen receptors for B cells.

IgE

Only 0.002% of total serum antibodies, bind tightly to receptors on mast cells and basophils, responsible for allergic reactions and useful against parasitic worms.

B Cells and Humoral Immunity

Activated B cells produce antibodies, process begins when B cells are exposed to free antigens, differentiate into plasma cells.

Clonal Selection

Each B cell produces only one kind of antibody. The appropriate antigen binds the cell, the cell proliferates into a clone, some become memory cells, others become plasma cells.

Antigen-Antibody Binding

Complex rapidly forms when antibody encounters the specific antigen, tags foreign cells for destruction. Mechanisms include agglutination, opsonization, neutralization, etc.

Immunological Memory

Antibody titer reflects the humoral response. Primary response involves IgM followed by IgG. Secondary response (memory or anamnestic) is intensified due to memory cells.

Monoclonal Antibodies

Produced from a hybridoma (fused cancerous B cell and antibody-producing B cell), can be grown indefinitely, all antibodies produced are the same.

Cell-Mediated Immunity

Based on the activity of T cells. Chemical messengers are cytokines. Interleukins communicate between leukocytes.

Major Histocompatibility Complex (MHC)

Expressed on mammalian cells. T-dependent antigens are presented with MHC to TH cell, which produces cytokines to activate B cells.

T Cells

Develop from stem cells in bone marrow, differentiate in the thymus, migrate to lymphoid organs. Main types: helper T cells (TH), cytotoxic T cells (TC), delayed hypersensitivity T cells (TD), suppressor T cells (TS).

Helper T Cells

Play central role in immune response, induce formation of cytotoxic T cells and macrophages.

Cytotoxic T Cells

Destroy target cells on contact.

Nonspecific Cellular Components

Activated macrophages (enhanced phagocytic capabilities) and natural killer cells (destroy virus-infected and tumor cells without prior stimulation).