Module 2.4 Adaptive Immunity

Adaptive Immunity

the body's ability to recognize and specifically target pathogens or foreign substances through a learned immune response, uses memory

Primary function of adaptive immune system

recognition of non-self substances, development of a targeted response, and retaining memory of pathogens for a faster response in the future

Components of Adaptive Immunity

T and B lymphocytes(T and B cells) and antibodies

Antigens

small molecules found on the surface of microbes, infected cells, or abnormal tissues

Clonal diversity

the process by which the extensive diversity of T and B cells is established

Antigen processing and presenting cells(APCs)

process antigens and present them on their surface so they can be recognized by T lymphocytes to initiate the immune response

macrophages, dendritic cells, and B cells

Humoral Immunity

one of two adaptive immune responses, antibodies circulate in the blood and defend against extracellular antigens, done by B cells and antibodies

Cell-mediated Immunity

one of two adaptive immune responses, T cells defend against intracellular pathogens and abnormal cells with help from NK cells and phagocytes, results in destruction of target cell

Exogenous antigens

extracellular non-self antigens that enter the body and circulate in blood and lymph

Endogenous antigens

intracellular non-self antigens that have been generated when the cell has become abnormal because of injury, infection, or mutation of its DNA

T and B Lymphocytes

recognize antigens from invaders and abnormal tissues, differentiate into effector cells, and provide memory

B-Cell Receptor(BCR)

complex of cell surface–bound antibody and other molecules involved in intracellular signaling, its role is to recognize a specific antigen and communicate this information to the cell’s nucleus

Clonal Selection

every lymphocyte is particular to an antigen and clones are created of this lymphocyte to attack the specific antigen

Tolerance

the ability of the adaptive immune system to remove or suppress adaptive immune responses to self-antigens or to innocuous non-self antigens

Major histocompatibility complex(MHC)

molecules that present antigens on the surface of APCs and abnormal cells, found on the surface of all human cells except RBCs

MHC I

found on all nucleated cells, antigens on these are recognized and bound by T-cytotoxic cells

MHC II

found only on APCs, antigens present on these are recognized and bound by T-helper cells

antigen processing and antigen presentation

the processes by which exogenous and endogenous antigens are cut up into small antigenic fragments and then presented to Tc cells (MHC I) or Th cells (MHC II)

T-helper cells

release cytokines and chemokines to activate B cells and cytotoxic T cells

T-regulatory cells(Treg cells)

secrete cytokines that suppress the immune system and promote tolerance

T-cytotoxic cells

directly kills infected and abnormal cells

Plasma cells

activated B cells that produce antibodies that are capable of detecting the identical antigen as was bound by the BCR

B-cells

produce antibodies for antigen neutralization, differentiate into plasma cells and memory B-cells

Antibody structure

Two heavy chains and two light chains forming variable and constant regions

Antibody functions

protection against infections, neutralization, opsonization, and complement activation

IgG antibody

most abundant antibody, does most of protective activity against infection, transported across the placenta during pregnancy, best opsonin

IgM antibody

largest antibody, first produced during the initial response to antigens, best complement-activating antibody

IgA antibody

found in blood and bodily secretions, prevents the attachment and invasion of pathogens through mucosal membranes

IgD antibody

functions as a part of the BCR antigen receptor on the surface of early B cells

IgE antibody

a mediator of many common allergic responses, a defense against parasitic infections

Neutralization

a direct antibody mechanism, inactivating or blocking the binding of antigens to receptors

Secretory(mucosal) immune system

partially independent immune system that protects the external surfaces of the body by secreting antibodies through various glands

Primary immune response

first interaction with antigen, initial production of IgM followed by production of IgG against the same antigen

Secondary immune response

second interaction with same antigen, more rapid production of larger amount of antibody than primary response, some IgM but a lot of IgG

Memory B and T cells

B and T cells differentiate into these during clonal selection, they remain inactive until subsequent exposure to the same antigen

Hypersensitivities

adaptive immunity disorder, allergic reactions

Autoimmunity

adaptive immunity disorder, immune response against the body’s own cells

Immunodeficiency

adaptive immunity disorder, inadequate immune response