Adaptive Immunity Lecture Notes

Flashcards on Adaptive Immunity

Antigen

Any substance that causes the immune system to produce antibodies against it; an abbreviation of antibody generator

Antigen Composition

Proteins or glycoproteins on the surface of a pathogen recognized by the immune system

Antigen Location

Found on the surface of foreign organisms or particles, including bacteria, viruses, toxins, foreign tissue, and even our own cells (self-antigens)

Antigen-Presenting Cells (APCs)

Cells that engulf and destroy pathogens, presenting antigens to T cells and B cells

Examples of APCs

Macrophages, dendritic cells, and B cells

Phagocytosis

The process by which APCs engulf and destroy bacteria or pathogens

Lysosomes

Vacuoles containing digestive enzymes that break down bacteria

MHC Proteins

Proteins produced by the cell that combine with antigens and are displayed on the cell surface

Lymphocytes

The primary cells involved in the adaptive immune response

Types of Lymphocytes

T cells, B cells, and Natural Killer (NK) cells

Lymphocyte Origination

Originate in the bone marrow and migrate to the thymus (for T cells) or bone marrow (for B cells) to mature

Immunocompetence

The process by which lymphocytes become able to be activated and recognize specific antigens

T Cells Role

Involved in cell-mediated immunity and the destruction of intracellular pathogens, cancerous cells, and foreign cells

B Cells Role

Involved in humoral immunity (antibody-mediated immunity) and the removal of extracellular pathogens

Humoral Immunity

Immune function performed by antibodies

B Cell Activation

Activated by intact antigens and differentiate into plasma cells and memory B cells; with the help of T helper cells

Plasma Cells

Cells that actively secrete antibodies

Memory B Cells

Cells that retain memory for specific antigens, enabling a rapid response upon second encounter

Antibody Function

Antibodies help defend against extracellular pathogens like bacteria

Cytotoxic T Cells

Require the help of T helper cells to differentiate into memory T cells and active T cells

Memory Cells Role

Facilitate rapid response to a second exposure to the same antigen

Plasma Cell Function

Activated B cells proliferate and differentiate into these; they are able to secrete around 2,000 antibodies over a short lifespan

Memory B Cells Function

Remember an antigen and can be rapidly activated if the antigen is encountered again

Secondary Immune Response

Occurs when the immune system is exposed to the same antigen again, leading to a much stronger and quicker immune response

Active Immunity

The body is involved in making antibodies; can be acquired through infection or vaccination

Passive Immunity

An individual receives antibodies produced elsewhere, such as through the placenta or breast milk

Passive Immunity Results

Immediate protection but no lasting protection because there is no formation of memory cells

Antibody Structure

Two heavy chains and two light chains

Complement Binding Site

Involved in activation of complement

Constant Region

Same in all antibodies

Variable Region

Creates the antigen binding site

Classes of Antibodies

IgG, IgA, IgM, IgE, and IgD

IgG

Major antibody in serum, able to cross the placenta

IgA

Found in secretions like saliva and breast milk

IgM

First antibody produced in response to a new antigen exposure

IgE

Involved in allergic and hypersensitivity responses

IgD

Found exclusively on the surface of B cells, involved in B cell sensitization and activation

Antibody Action

Bind to antigens and clump them together to enhance phagocytosis

Opsonisation

Coat antigens and bind to phagocytes to facilitate phagocytosis

Neutralisation of Toxins

Mask the sites toxins use to bind to cells, neutralizing the toxin

Activation of Complement Proteins

Form membrane attack complexes (MACs) that create holes in bacterial membranes, leading to cell lysis

Stimulation of Inflammation

Triggers the release of histamine granules, mediating inflammation

Cytotoxic T Cells

Killers: removes pathogens and infected host cells

Helper T Cells

Helps activate B cells and other T cells

Regulatory T Cells

Calm down: Reduce auto immune disease by distinguishing cells