Module 17: Immune Response Part II Adaptive Defenses

Vocabulary flashcards covering the components and processes of the adaptive immune response, including cell types, MHC classes, antibody types, and forms of immunity.

Specific

A characteristic of adaptive defenses where the system recognizes and responds to a specific antigen.

Systemic

A characteristic of adaptive defenses indicating the response is system wide rather than local.

Memory

The ability of the immune system to remember an antigen and respond stronger and faster upon subsequent exposures.

Antigens

Any substance that induces an immune response.

Immunogenicity

A measure of the ability of an antigen to induce an immune response.

Antigenic determinants

The specific site on an antigen that an antibody binds to.

Self antigens

Antigens that allow the immune system to recognize cells as self.

Major histocompatability antigens (MHC)

Surface proteins encoded by MHC genes used for self-recognition.

MHC Class I

MHC proteins found on all cells except red blood cells (RBC's).

MHC Class II

MHC proteins found on activated immune system cells, including B cells, dendritic cells, macrophages, and thymic epithelial cells.

B lymphocytes

Immune cells that originate and mature in the bone marrow.

T lymphocytes

Immune cells that originate in the bone marrow and mature in the thymus.

Positive selection

The process that identifies T cells capable of recognizing self MHC.

Negative selection

The process of eliminating T cells that react to self MHC and self antigen, leading to apoptosis.

Self tolerance

The property of immune cells where they do not attack self cells unless the cells are abnormal.

Apoptosis

Programmed cell death.

Antigen presenting cells

Cells such as dendritic cells, macrophages, and B cells that present antigens with MHC II to the immune system.

Clonal selection

The process of selecting specific B cell(s) for an antigen and causing them to multiply.

T Helper Lymphocyte

A cell with a T cell receptor that binds to MHC II and antigen; it secretes interleukin 4 to stimulate B cell proliferation and differentiation.

MHC Class II restricted

A requirement where a T cell must bind to a macrophage presenting MHC II to become activated.

Plasma cells

Differentiated B cells that act as antibody factories and do not have B cell receptors (BCR's).

Memory cells

Cells that remain in circulation to provide a faster and stronger response upon re-exposure to an antigen.

Primary immune response

The initial response taking $3-5$ days for the titer to increase, lasting about 3 weeks, and involving IgM followed by IgG.

Secondary immune response

A response with a shorter lag where IgM and IgG are produced simultaneously at a higher titer and for a longer duration.

Variable region

The part of the basic antibody structure that binds to the antigen.

Constant region

The part of the antibody structure that binds to complement and host cells.

IgA

An antibody class that exists as a monomer in serum and a dimer in secretions like mucus, milk, and tears.

IgM

An antibody class that is a pentamer and remains in blood circulation.

IgD

Antibodies that serve as membrane-bound antigen receptors.

IgG

The typical Y-shaped antibody representing $85\%$ of antibodies; involved in opsonization, neutralization, and complement activation.

IgE

Y-shaped antibodies that attach to receptors on eosinophils, mast cells, and basophils.

Monoclonal antibodies

Identical antibodies used in diagnostics and test kits.

Cytotoxic T cells (CD8)

T lymphocytes that are MHC Class I restricted and responsible for the lethal hit to target cells.

MHC Class I restricted

A condition where the T cell receptor (TCR) is specific for the MHC I and endogenous antigen complex.

Co-stimulation

The use of cytokines like IL1 and IL2 to stimulate the T cell to continue its response after antigen binding.

Cytokines

Chemical messengers that act as intercellular signals.

Lethal hit

The process leading to the lysis of a target cell.

Perforin

Molecules that create transmembrane pores in the target cell, similar to the complement membrane attack complex (MAC).

Lymphotoxin

A substance that fragments the DNA of a target cell.

$$\gamma \text{ (Gamma) Interferon}$$

A cytokine that stimulates macrophages to reach killer status.

Naturally acquired active immunity

Immunity resulting from natural exposure to a pathogen.

Artificially acquired active immunity

Immunity induced by vaccines.

Subunit (second generation vaccines)

Vaccines containing only pieces of the microorganism rather than the entire organism.

Synthetic (third generation vaccines)

Genetically engineered vaccines where another organism produces the subunit, such as the HBV vaccine.

Adjuvants

Substances added to vaccines to increase efficacy, such as aluminum sulfate (alum), aluminum hydroxide, mineral oil, and peanut oil.

Herd immunity

A state where the majority of a population is immunized, making it unlikely for susceptible individuals to encounter the disease.

Thimerosal

A mercury-containing preservative used in some vaccines.

Naturally acquired passive immunity

Immunity provided by maternal antibodies passed to an offspring.

Antiserum

A form of artificially acquired passive immunity.