Study Guide: Specific Immune Response and Humoral Immunity ~ Chp 17

Specific Immune Response

I. Properties

The specific immune response is a critical component of the adaptive immune system, characterized by its ability to recognize and remember specific pathogens. This system provides targeted defense against infections and is essential for long-term immunity.

• Specificity: The immune response targets particular antigens, allowing for precise recognition and elimination of pathogens.

• Memory: After initial exposure, the immune system retains a memory of the antigen, enabling a faster and stronger response upon subsequent exposures.

II. Types of Specific Immunity

Specific immunity can be acquired through various means, each providing protection against pathogens in different contexts.

• 1. Naturally acquired active immunity: Immunity developed after exposure to a pathogen through infection; the body produces its own antibodies and memory cells.

• 2. Naturally acquired passive immunity: Immunity gained by receiving antibodies from another individual, such as maternal antibodies transferred to a fetus via the placenta.

• 3. Artificially acquired active immunity: Immunity developed after exposure to antigens through vaccination; stimulates the body to produce its own antibodies and memory cells.

• 4. Artificially acquired passive immunity: Immunity gained by receiving antibodies from an external source, such as injection of antiserum.

III. Humoral Immunity

Humoral immunity involves the production of antibodies by B cells, which circulate in body fluids to neutralize pathogens. This branch of immunity is essential for defending against extracellular microbes.

• Antigens, epitopes, haptens:

  • Antigen: Any substance that can induce an immune response.

  • Epitope: The specific part of an antigen recognized by antibodies.

  • Hapten: A small molecule that, when combined with a larger carrier, can elicit an immune response.

• Antibody constant region: Conveys a variety of properties onto the different classes of antibody proteins, determining their function and location.

Antibody Class	Key Properties	Location/Function
IgG	Crosses placenta, fixes complement	Main antibody in blood; provides long-term immunity
IgM	First antibody produced, pentamer	Primary response to infection
IgA	Secretions: mucus, saliva, milk, dimer	Protects mucosal surfaces
IgE	Binds to mast cells and basophils, triggers histamine release	Allergic responses, defense against parasites

• B cells: Responsible for humoral immunity and cellular immunity. Upon activation, B cells differentiate into plasma cells (antibody-secreting cells) or memory cells.

• TH cells: Helper T cells have CD4 receptors, which are essential for HIV attachment. These cells present antigen to B cells, aiding in the specific antibody response.

IV. Cellular Immunity

Cellular immunity is mediated by cytotoxic T lymphocytes (CTLs), which target and destroy infected or abnormal cells. This response is crucial for eliminating cells harboring intracellular pathogens, such as viruses.

• CTL cells: Possess the same specificity as antibody surveillance, binding to and destroying target cells through cytolytic processes.

V. Cytokines

Cytokines are signaling proteins released by cells to communicate and coordinate immune responses. They play vital roles in regulating the intensity and duration of immune reactions.

• Interleukins: Communicate between leukocytes (white blood cells), facilitating immune cell interactions.

• Chemokines: Induce migration of leukocytes to infected areas, promoting inflammation and immune cell recruitment.

• Interferons: Interfere with viral infection by inhibiting viral replication and activating immune cells.

VI. Miscellaneous

This section covers additional important concepts and applications in immunology.

• Monoclonal antibodies: Laboratory-produced molecules engineered to serve as substitute antibodies; used in diagnostics and therapy. Example applications: Fluorescent microscopy, ELISA.

• Systemic anaphylaxis: A severe, potentially life-threatening allergic reaction (anaphylactic shock) that requires immediate medical attention.

• Erythroblastosis fetalis (Hemolytic Disease of the Newborn, HDN): A condition where maternal antibodies attack fetal red blood cells, leading to anemia in the newborn.

Additional info: Monoclonal antibodies are produced by fusing a specific B cell with a myeloma cell to create a hybridoma, which can be cultured to produce large quantities of identical antibodies. ELISA (Enzyme-Linked Immunosorbent Assay) is a common laboratory technique used to detect the presence of antibodies or antigens in a sample.