Immunology 1: Intro to Immune System

Immune system

Collection of molecules, cells, and tissues that work together in establishing immunity

Immunity

State or quality of being protected from the invasion of foreign organisms

Antigens, Ags

Living microorganisms, microbial toxins, and microbial byproducts

Pollen, pet dander, and chemicals

Aged, damaged, and mutant cells in the host

Physical barriers, secretions, phagocytosis, complement pathway

Types of innate immunity

Innate immunity

First line of defense

Secretion

Traps, washes off, and destroys Ags

Tears, saliva, sweat, gastric acid, and other body fluids

Lysozymes

Secretions contain enzymes that kill bacteria called ___ that prevent bacterial colonization and growth

Opsonization

Tags and glues bacteria to immune cells for easier phagocytosis

Inflammation

Induces immune cell recruitment and activation

Lysis

Directly kills bacteria by MAC formation

Allergens

Ags that can cause an allergic reaction in sensitive individuals

Humoral immunity, cell-mediated immunity

Forms of adaptive immunity

Humoral immunity

Adaptive immunity

B-cells and plasma cells

Antibodies (Abs)

Cell-mediated immunity

Adaptive immunity

CD8 T-cells

CD4 T-cells

Neutrophils, macrophages

Main phagocytes

Antibody (Abs)

Soluble protein

Immunoglobulin (Ig) = ___

B-cell receptor (BCR)

Ab anchoring the surface of B-cells

Plasma cells

After Ag recognition, B-cells differentiate into ___, the main Ab producers.

Epitope

Site within antigens to which Ag receptors bind

An Ag can have multiple of these

Antigenic determinant

An Ab recognizes only its specific ___, not others.

Innate immunity

Rapid response within hours

Fixed (<100 Ag receptor repertoire)

Limited number of specificities

Constant during the course of response

Adaptive immunity

Slow response in days to weeks

Variable (>10^9 Ag receptor repertoire)

Numerous highly selective specificities

Improve during the course of response (memory)

CD8 T-cells

Alternative names: Cytotoxic T-cells (Tc); cytotoxic T-lymphocytes (CTLs)

MHC class I

Intracellular or endogenous Ags (viral Ags)

Kill virus-infected cells

CD4 T-cells

Alternative name: Helper T-cells (Th)

MHC class II

Extracellular or exogenous Ags (bacterial Ags)

Help other immune cells to clear viruses, bacteria, and parasites

Pattern recognition receptors (PRRs)

In innate immunity

Recognize pathogen-associated molecular patterns (PAMPs)