Specific Resistance = Immunity Lymphocytes (review) Antigens & Antibodies Acquired Immunity Humoral Immunity: B-cell Function Cell Mediated Immunity: T-cell Function Stages of Disease Development

Lymphocyte 100 million produced per day therefore others must die (apoptosis = programmed cell death) B cells: Interact with antigens; may develop a clonal population of memory cells or become stimulated, divide and mature into antibody producing plasma cells. Antibody functions are called Humoral Immunity. T cells: Act as either “helpers” in communicating the presence of an antigen; or cytotoxic agents to destroy infected cells. These functions are called Cell-Mediated Immunity.

Antibody Monomer Structure: Many possible antibodies with different antigenic binding sites due to variable region diversity of long and short chains. Immunoglobin (Ig) = antibody

Antigen-Antibody Interaction Antigen = a substance with unique 3D form that causes antibody formation in B cells (lymphocytes). Antigens may possess one or more types of reactive molecular components; antigenic determinants or epitopes. Antigen binding sites on the antibody Fab fragments specifically recognize and chemcially interact with an epitope. Because a single antibody recognizes a single epitope, there may be multiple antibodies generated against an antigen with more than one epitope

Antigens can be components of whole microbes or viruses.

Antigens can be derived from very small molecules called haptens, which without some carrier molecule or cell would not elicit an immune response alone. This is the case for many drugs and/or toxins (e.g. some venoms). Think of a heptan as functioning as an incomplete antigen.

Antibody Classes IgG (80%; monomer; passive to fetus/newborn); IgM (<10%, pentamer of IgG, effective in agglutination); B cell surface involved in activation.) IgA (< 15%; dimer; released into fluid/mucus secretions); IgD (minor; monomer; on B cell surface involved in activation, blood and lymph). IgE (minor; monomer; on mast cells and basophils; involved in allergic response).

vaccine antiserum Passive = antibodies supplied to host from external sources, possibly prior to the presence of any foreign antigen in the host. Active = Foreign antigen introduced to host, which then stimulates immune response.