Immunology: T Cells, Antigens, and Antibodies

Flashcards covering the mechanisms of T and B cell activation, antibody classes, antigen characteristics, and the differences between primary and secondary immune responses based on the lecture transcript.

CD8 killer T cell

A T cell that requires antigen presentation on MHC class I and cytokine help from CD4 T cells to kill infected self-cells or cancer cells.

Rule of eights

A mnemonic used to remember MHC interactions: $CD8 \times MHC \text{ class } 1 = 8$ and $CD4 \times MHC \text{ class } 2 = 8$.

CD4 T cell

A helper T cell, described as a "mob boss," whose job is to secrete cytokines that activate or approve the "hit" by other immune cells.

Perforins

Enzymes that poke holes in a self-cell membrane to allow for the entry of granzymes.

Granzymes

Chemicals secreted by CD8 T cells that initiate the apoptotic cascade to break a cell down into smaller components.

Antigen

Anything that is immunogenic and can be recognized by lymphocytes.

Hapten

A structure so small that it is not antigenic on its own and must be complexed with a larger structure to be detected by the immune system.

Epitope

The specific small part of an antigen that is recognized by immune receptors and loaded into MHC molecules.

Super antigen

A substance, such as toxic shock syndrome toxin, that binds outside the normal MHC pocket between the beta chain and the MHC, causing massive, non-specific T cell activation.

Autoantigen

A self-substance that triggers an immune response against the body's own cells when tolerance fails.

Opsonization

The process of coating bacteria with antibodies or complement proteins to increase the effectiveness of phagocytosis by macrophages.

Neutralization

The blocking of a microbe's ability to bind to host cells, effectively preventing viral or bacterial infection.

IgM

The first antibody class made during an immune response; it is a large pentamer with 10 binding sites and can serve as a B cell receptor.

Affinity maturation

A change to the variable region of an antibody that increases its binding strength or "grip" for a specific epitope.

Isotype switching

Also known as class switching, this is a cytokine-driven process that changes the Fc region of an antibody, such as changing from IgM to IgA, IgD, or IgE.

IgG

The antibody most common in the secondary immune response; it provides memory and is highly specific due to affinity maturation.

IgA

A specialized antibody found in mucosal sites, including breast milk, lungs, and the intestines.

IgE

An antibody class involved in the allergic triad and the response against parasitic worms.

Allergic triad

The group of three cell types containing granules with histamine: mast cells, basophils, and eosinophils.

Primary response

The initial encounter with a microbe featuring a lag time of $10$ to $12$ days before the production of IgM and IgG.

Secondary response

The immune response following a second exposure or vaccination, characterized by the absence of lag time and a significantly higher quantity of specific IgG.

Titer

A measurement or count of antibodies used to prove immunity to specific pathogens.