Chapter 17: Adaptive Immunity (PART ONE)

adaptive immunity

involves a range of defenses that target specific pathogens after exposure

adaptive immune system is used

only when innate defenses (physical barriers like skin, mucous membranes, phagocytes, & inflammation) fail to stop a microbe

primary response

the initial immune response to a specific antigen, resulting in the production of antibodies and memory cells

secondary response

the immune response that occurs upon re-exposure to the same antigen, characterized by a faster and more effective production of antibodies due to memory cells

memory

exclusive component to the adaptive immune system

humoral immunity

a type of adaptive immunity that involves the production of antibodies by B cells to to combat antigens; takes place in extracellular fluid

immunoglobulin (Ig)

another name for antibody; bind to foreign molecules (antigens) and brings about humoral immunity

B cells

lymphocytes that are created in red bone marrow; process antigens (APC) and make anitbodies

dual system

describes the humoral & cellular components of the adaptive immune systems

cellular immunity (cell-mediated)

a type of adaptive immunity that involves the activation of T cells to defend against intracellular pathogens, such as viruses and certain bacteria; produces T lymphocytes & involves TCRs

T lymphocytes (T cells)

recognize antigenic peptides processed by phagocytic (APC) cells; mature in the thymus

T cell receptors (TCRs)

on the T cell surface that contact antigens, causing the T cells to secrete cytokines instead of antibodies

how B and T cells differentiate

thymus → T cell, remain in red bone marrow → B cell; both cells originate from stem cells in adult red bone marrow (or fetal liver)

antigens

substances that cause the production of antibodies

• usually components of invading microbes or foreign substances

• interact with epitopes, or antigenic determinants, on the antigen

haptens

antigens too small to provoke immune responses; attach to carrier molecules

5 classes of Ig (humoral immunity)

GMADE

antibody structure (be able to ID)

Y shape; includes constant region, variable region, heavy chain, light chain, held together by disulfide bridges

major histocompatibility complex (MHC)

genes encode molecules on the cell surface

MHC I (in cell-mediated response)

are on the membrane of nucleated animal cells; can identify “self”

MHC II (in humoral response)

are on the surface of antigen-presenting cells (APCs). including B cells

humoral vs. cell-mediated immunity

humoral immunity produces antigen-specific antibodies and is primarily driven by B cells (includes the 5 Ig classes and MHC II); cell-mediated immunity does not depend on antibodies for its adaptive immune functions and is primarily driven by mature T cells, macrophages and the release of cytokines in response to an antigen (includes MHC I)

activation of B cells to produce antibodies (be able to write steps)

• initiation: B cell internalizes pathogen and presents on MHC II

• communication: T_H cell recognizes MCH II/anitgen complex and releases cytokines

• activation: B cell activates to plasma cell + makes and releases antibody specific to antigen

T-dependent antigen

antigen that requires a T_H cell to produce antibodies

T-independent antigens

• stimulate the B cell without the help of T cells

• provoke a weak immune response, usually producing IgM

• no memory cells generated

antigen–antibody complex

forms when antibodies bind to antigens

• strength of bond is the affinity

• protects the host by tagging foreign molecules or cells for destruction

IgG

primary antibody, most abundant; fetus/newborn antibody

IgM

pentamer; aggregate organisms

IgA

dimer; mucosal membranes

IgD

surface B cells; start humoral response

IgE

larger antibodies; parasitic infections