Study Notes on Humoral Immunity and Immune Disorders

Humoral Immunity Overview

• Immunocompetent B cells possess numerous surface receptors for specific antigens.

• Antigen binding facilitates receptor-mediated endocytosis and processing of antigens with MHC–II.

B Cell Activation and Response

• Clonal selection activated by T h2 cells recognizing the MHCII/antigen complex.

• B cells proliferate into plasma cells that secrete antibodies and memory B cells.

• Primary response is the initial encounter with pathogens; secondary response is faster and more robust due to memory cells.

Antibody Structure

• Antibodies (Immunoglobulins) consist of four polypeptide chains linked by disulfide bonds.

• Structure includes variable (V) regions (antigen binding sites) and constant (C) regions (isotype determination).

Classes of Antibodies

• IgD, IgM (pentamer), IgG, IgA (dimer), IgE (monomer).

• Different classes have specific roles in immune defense.

Antibody Functions

• Antibodies neutralize, agglutinate, and precipitate antigens.

• They activate complement systems for further immune response.

Adaptive Immunity Summary

• Utilizes recognition of antigens and intercellular communication among immune cells for effective response.

Immune Disorders

• Disorders include immunodeficiency, autoimmune diseases, and hypersensitivities.

• Types of immunodeficiencies: congenital (e.g. SCID) and acquired (e.g. AIDS).

Hypersensitivity Types

• Four types: Type I (IgE-mediated), Type II (IgG and IgM), Type III (immune complex), and Type IV (delayed-type).

Autoimmune Diseases

• Characterized by the immune system failing to distinguish self and nonself.

• Examples: multiple sclerosis, rheumatoid arthritis, lupus.

Allergies and Hypersensitivity Mechanisms

• Allergies often involve IgE responses, leading to anaphylaxis and other allergic reactions.

• The hygiene hypothesis suggests environmental factors influence allergy prevalence.