Adaptive Immune System Flashcards

Flashcards on Adaptive Immune System

Innate Immune System

Present in all plants, invertebrates & vertebrates; Non-specific recognition – no specific memory response

Adaptive Immune System

Vertebrates only; Specific recognition - ability for memory response

B lymphocytes

Secrete antibodies (immunoglobulins)

CD4+ T lymphocytes

Helper T lymphocytes

CD8+ T lymphocytes

Cytotoxic T lymphocytes

Lymphocyte Development

B cells develop in the bone marrow; T-cell progenitors arise in the bone marrow and migrate to the thymus

Antigen

Any substance that can bind to specific lymphocyte receptors and so induce an immune response

B-cell receptor (BCR)

Surface transmembrane immunoglobulin; antigen receptor on B lymphocytes

T-cell receptor (TCR)

Surface transmembrane immunoglobulin; antigen receptor on T lymphocytes

B cell receptor interaction

Interact with Antigen; Each B cell has 200-500,000 identical BCRs on its surface

Antibodies

Soluble BCRs

Generic Structure of an Antibody

Antibody monomers consist of 2 heavy and 2 light polypeptide chains

Variable region

Antigen binding region

B cell activation

Cross-linked BCRs help activate B lymphocytes

T cell receptors

Interact with antigenic peptides in Major Histocompatibility Complex (MHC) molecules

MHC class I

Presents mostly intracellular antigens; Helps detect and kill infected cells (e.g. viral)

MHC class II

Presents mostly extracellular antigens; Helps respond to extracellular and intraceullar infections

MHC class I molecules

CD8+ T cells only interact with this molecule; present on nearly all cells; Function is T cell mediated killing

MHC class II molecules

CD4+ T cells only interact with this molecule; present on Dendritic cells, Macrophages, B cells; Function is T-cell mediated help cytokine release activating B cells etc.

Cytotoxic T lymphocyte (CTL)

Major effector cell of adaptive immune system; Requires activation first in lymphoid tissues via MHC class I/TCR interaction

Two mechanisms of killing by CTL

Perforin/Granzyme Killing; FAS mediated Killing

Cytokine interleukin (IL)-2

Released and its receptor expressed during an infection when T and B cells divide, driving T-cell proliferation

Memory B and T cells

Allow immune response in a 2nd exposure to be: Faster, Larger, More efficient, More effective