1. Introduction to Immunology – Foundational Concepts & Vocabulary

These vocabulary flashcards cover key immunology concepts from the lecture, including immune system functions, antigen properties, MHC genetics, and major cell types and responses.

Immune System Functions

Identification of pathogens and self, tumor surveillance, immunological memory, hypersensitivity reactions, tolerance maintenance, and response to immunodeficiency.

Antigenic determinant

Epitope that is a molecular structure on the surface of an antigen that is recognised by componets of the immune system.

Major Histocompatability (MHC) tissue compatibility

In humans these are a cluster of genes called Human Leukocyte Antigens (HLA) genees and the proteins they encode. They are located on chromosome 6, codominant inheritence.

Minor Histocompatability Antigens

Peptides or celluar protiens that bind to MHC molecules. These are endoded by genes located outside the HLA. It is not currently possible to indentify them in the lab.

MHC II

Are on APC and their function is to present a forgein antigen. e.g. a bacterial antigen after an APC has ingested a bacterium and broken it down. They interact with CD4+ T cells to activate the immune response.

MHC I

Found on most cells of the body. Their fuctions are to present self-antigen and thus annouce “I am healthy” and to present a foreign antigen, e.g. an antigen from a virus that has injected a cell or a cancer antigen.

Pathogen

Any disease-causing microorganism such as a virus, bacterium, parasite, or fungus recognized as foreign by the immune system.

Tumor Surveillance

Immune system process that detects and destroys emerging cancer cells before they form tumors.

Immune Memory

Long-lasting ability of the immune system to recall a pathogen and mount a faster, stronger response upon re-exposure.

Hypersensitivity Diseases

Overactive immune reactions, including allergies and autoimmune disorders, that damage host tissues.

Immune Tolerance

State in which the immune system does not mount a response against self-antigens or specific tolerated antigens.

Immunodeficiency

Condition where parts of the immune system are absent or non-functional, leading to increased infection risk.

Antigen

Any substance that can bind immune receptors and may provoke an immune response.

Immunogenicity

Capacity of an antigen to activate the immune system and induce antibody or T-cell responses.

Tolerogen

Antigen that binds immune receptors but fails to elicit, or actively inhibits, an immune response.

Human Leukocyte Antigens (HLA)

Name for human MHC proteins located on chromosome 6; inherited codominantly.

Codominant Expression

Simultaneous expression of maternal and paternal MHC alleles on the same cell.

Locus

Physical location of a gene on a chromosome (e.g., HLA-A, ‑B, ‑C in MHC I).

Allele

Alternative version of a gene at a particular locus (e.g., HLA-A*02:01).

Haplotype

Set of MHC alleles inherited together from a single parent.

Peptide-Binding Groove

Region of MHC molecule that accommodates antigenic peptides for T-cell recognition.

Antigen-Presenting Cell (APC)

Cell type (dendritic cell, macrophage, B cell) that processes antigen and displays it on MHC to T cells.

Dendritic Cell

Professional APC specialized in initiating primary T-cell responses. Found in lymphoid tissue, connective tissues and epithelium.

Macrophage

Phagocytic APC that ingests pathogens and presents antigens, also functioning in innate immunity. Found in lymphoid tissue, connective tissues and body cavities.

B Cell

Lymphocyte that produces antibodies and can present antigen via MHC II to helper T cells. Found in lymphoid tissue and blood.

T Helper Cell (CD4⁺)

T lymphocyte that recognizes antigens on MHC II and coordinates immune responses.

Natural Killer (NK) Cell

Cytotoxic lymphocyte that kills virus-infected or transformed cells without prior sensitization.

Humoral Response

Branch of adaptive immunity mediated by antibodies produced by B cells.

Cellular Response

Adaptive immune arm involving T cells that kill infected cells or help other immune cells.

Phagocytosis

Engulfment and digestion of microbes or particles by cells like macrophages and neutrophils.

Primary Immune Response

First exposure reaction requiring clonal expansion; slower and lower magnitude.

Secondary Immune Response

Subsequent exposure reaction that is quicker and stronger due to memory cells.

Active Vaccine

Preparation of antigen that stimulates the immune system to generate memory and protective immunity.

Differential MHC Distribution

Variable expression of MHC I on nearly all nucleated cells and MHC II mainly on APCs, reflecting their functions.

Self/Non-Self Discrimination

Fundamental immune ability to recognize host molecules as self and foreign entities as non-self.

Immune System Diversity

Capacity to respond to a vast array of antigens through diverse receptors and antibodies.