Immunology Study Guide Flashcards

These flashcards cover key concepts related to immunology, specifically focusing on antigen capture and presentation, T and B cell activation, immune responses, and antibody mechanisms.

Antigen Presenting Cells (APCs)

Cells that capture and present antigens to T cells, primarily dendritic cells and macrophages.

Dendritic Cells

APCs that are more effective than macrophages at stimulating naïve CD4 T cells.

Phagocytosis

The process by which APCs capture antigens at infection sites.

MHC Genes

Major Histocompatibility Complex genes that are polymorphic and show co-dominant expression.

MHC Class I Genes

Includes HLA-A, HLA-B, HLA-C.

MHC Class II Genes

Includes HLA-DP, HLA-DQ, HLA-DR.

Protein Structure of MHC Class I

Composed of an alpha chain plus beta2-microglobulin.

Protein Structure of MHC Class II

Composed of an alpha chain plus a beta chain.

Peptide Binding Pocket

The structure formed by amino-terminal domains of MHC molecules that binds peptide antigens.

CD4 T Cells

Helper T cells that bind to MHC Class II molecules.

CD8 T Cells

Cytotoxic T cells that bind to MHC Class I molecules.

Peptide Binding Stability

MHC proteins are unstable unless bound to a short peptide, typically 5–15 amino acids.

Immunodominance

Focusing of the immune response on a small subset of microbial peptides.

Class II Pathway

Antigen processing pathway that involves phagocytosed material in endosomes.

Invariant Chain (Ii)

Protein that helps in the proper folding and assembly of MHC Class II in the ER.

Peptide Loading Class II

HLA-DM removes CLIP to allow peptide binding in lysosomes.

Class I Pathway

Antigen processing pathway for intracellular proteins processed by the proteasome.

Ubiquitin

A small protein that tags intracellular proteins for degradation.

TAP transporter

Transporter that allows peptide fragments to enter the ER for Class I MHC loading.

Lymphocyte Development

The process of maturation for B and T cells in their respective tissues.

B Cell Receptor Structure

Consists of 4 polypeptide chains, including Heavy and Light chains.

Variable Domains

Parts of the BCR that form antigen-binding regions and have high variability.

Complementary Determining Regions (CDRs)

Regions of highest variability in BCR and TCR crucial for antigen recognition.

Isotype Determination

The function of the constant region of antibodies in determining their type and biological function.

IgG

The most abundant antibody in blood, performing a wide range of biological functions.

IgA

An antibody important for mucosal immunity; exists as a dimer.

IgM

The first antibody to be secreted; exists as a pentamer and has a large binding capacity.

IgE

An antibody associated with allergic reactions and anti-helminth immunity.

IgD

An antibody present in trace amounts in blood.

T Cell Receptor Structure

A heterodimer made of an alpha chain and a beta chain that recognizes antigens.

Linear Peptide Recognition

The TCR recognizes linear, processed peptides bound to MHC.

Costimulation

The additional signals required for T cell activation, particularly through CD28 and B7.

Checkpoint Inhibition

Mechanisms such as CTLA-4 and PD-1 that inhibit immune responses.

ZAP-70

A tyrosine kinase recruited to phosphorylate signaling components following TCR activation.

Calcium Signaling

Intracellular calcium increase is crucial for T cell activation and transcription.

NFAT

A transcription factor activated by calcium signaling that promotes IL-2 expression.

T Helper Cell Differentiation

The process by which activated T cells develop into different functional subsets.

Th1 Cells

T helper cells that secrete IFN-gamma and activate macrophages.

Th2 Cells

T helper cells that secrete IL-4, IL-5, and IL-13, important for anti-helminth responses.

Th17 Cells

T helper cells that secrete IL-17 and recruit neutrophils.

CD8 Cytotoxic T Cells

T cells that kill infected cells through apoptosis.

Perforin and Granzymes

Cytotoxic molecules released by CTLs to induce apoptosis in infected cells.

Regulatory T Cells (Tregs)

T cells that maintain tolerance to self-tissues and regulate immune responses.

B Cell Activation

The process through which B cells recognize and respond to antigens.

Thymus-Independent Antigens

Non-protein antigens that stimulate B cells without T cell help, typically leading to IgM production.

Primary Immune Response

Initial immune response characterized by slower kinetics and lower affinity IgM production.

Secondary Immune Response

Faster immune response characterized by affinity-matured IgG production.

BCR Signaling Pathway

Activation of B cells involves cross-linking of BCRs and accessory proteins, leading to signal transduction.

T-B Cell Interaction

Activated B cells migrate to T cells and present antigens for help in activation.

Germinal Center Reactions

Processes in lymph nodes where B cells undergo affinity maturation and isotype switching.

Activation Induced Deaminase (AID)

An enzyme essential for isotype switching and somatic hypermutation in B cells.

Affinity Maturation

Selection of B cells with the highest affinity for antigens during germinal center reactions.

Antibody Effector Mechanisms

Ways antibodies directly and indirectly neutralize pathogens.

Opsonization

Antibodies coat pathogens to enhance phagocytosis via Fc receptors.

ADCC (Antibody-Dependent Cellular Cytotoxicity)

Mechanism where NK cells kill target cells bound by antibodies.

Fc Receptors

Receptors on immune cells that bind the Fc region of antibodies to mediate immune functions.

Complement System

Part of the immune system that enhances the ability of antibodies to clear pathogens.

Poly-Ig Receptor

Transports IgA across epithelial tissues into secretions.

FcRn (Neonatal Fc Receptor)

Transports IgG across the placenta, providing passive immunity to the fetus.