Immune System Science Olympiad Competition Practice Flashcards

Vocabulary-style flashcards covering the anatomy, physiology, mechanisms, and disorders of the immune system for Science Olympiad Division C preparation.

Innate Immunity

A fast-acting, nonspecific branch of the immune system that recognizes conserved molecular patterns and consists of the first and second lines of defense without generating classical memory.

Adaptive Immunity

A highly specific branch of the immune system involving B and T cells that generates antigen-specific receptors and long-lasting memory.

Bone Marrow

A primary lymphoid organ and the site of hematopoiesis where B lymphocytes mature and T cell precursors originate.

Thymus

A primary lymphoid organ located in the anterior superior mediastinum where T cells undergo maturation and positive/negative selection.

Spleen

A secondary lymphoid organ that filters blood; its white pulp contains lymphocytes for immune surveillance and its red pulp removes old or damaged RBCs.

Lymph Nodes

Secondary lymphoid organs that filter lymph and provide sites for antigens, APCs, B cells, and T cells to interact.

Neutrophil

The most abundant white blood cell; a granulocyte with a multilobed nucleus that performs rapid phagocytosis during acute inflammation.

Eosinophil

A granulocyte with a bilobed nucleus and red-orange granules involved in parasite defense and allergic reactions.

Natural Killer (NK) Cell

An innate lymphocyte that kills virus-infected and tumor cells by detecting reduced MHC class I expression and using perforin or granzymes.

B Lymphocyte

A component of adaptive immunity that recognizes intact antigens and differentiates into antibody-secreting plasma cells or memory cells.

T Lymphocyte

A component of adaptive immunity that recognizes processed peptide fragments on MHC molecules and coordinates cell-mediated responses.

Plasma Cell

A terminally differentiated B cell specialized for the high-rate secretion of antibodies.

MHC Class I

Molecules found on nearly all nucleated cells that display intracellular/endogenous proteins to CD8+ cytotoxic T cells.

MHC Class II

Molecules expressed mainly on professional antigen-presenting cells (APCs) that display extracellular proteins to CD4+ helper T cells.

Antigen

A molecule or molecular region capable of being specifically recognized by antibodies or lymphocyte receptors.

Epitope

The specific portion of an antigen that is bound by an antibody or T-cell receptor-MHC complex.

IgM

A pentameric antibody that is the first major class secreted in a primary response; it is excellent at agglutination and complement activation.

IgG

The most abundant antibody in blood and tissue which can cross the placenta and is the main antibody of the secondary response.

IgA

An antibody dimer found in mucosal secretions like saliva, tears, and breast milk that protects mucosal surfaces.

IgE

An antibody bound to mast cells and basophils that triggers histamine release for immediate allergy and parasite defense.

Complement System

A group of proteins that enhances immunity through opsonization (C3b), inflammation (C3a, C5a), and lysis (MAC formed by C5b-C9).

Inflammation Signs

The five classic indicators caused by vasodilation and increased permeability: redness (rubor), heat (calor), swelling (tumor), pain (dolor), and loss of function.

Pyrogens

Substances that stimulate the production of prostaglandin E2 in the hypothalamus to raise the body's temperature set point, causing fever.

Type I Hypersensitivity

An immediate allergic reaction involving IgE cross-linking on mast cells, leading to rapid mediator release like histamine.

Type IV Hypersensitivity

A delayed-type hypersensitivity mediated by T cells rather than antibodies, typically occurring $48$-$72$ hours after exposure.

Active Immunity

Long-lasting protection developed when a person's own immune system responds to an antigen, such as through natural infection or vaccination.

Passive Immunity

Immediate but temporary protection provided by the transfer of preformed antibodies, such as maternal antibodies or injected immunoglobulin.

HIV

A virus that primarily infects CD4+ T cells, macrophages, and dendritic cells by binding to CD4 and a co-receptor like CCR5 or CXCR4.

Graft-versus-host disease

A condition where donor immune cells from a transplant (especially bone marrow) attack the recipient tissues.

IL-1

An endogenous pyrogen produced by macrophages and dendritic cells that promotes inflammation and fever.

Type I Interferons

Cytokines ($IFN-\alpha$ and $IFN-\beta$) produced by virus-infected cells to induce an antiviral state in neighboring cells.