MP2024-ImmuneSystem2.pptx

4 functions of Adaptive immune (specific defense) systems

1. Protects against infectious agents & abnormal body cells

2. AMplifies inflammatory response

3. Activates complement

4. Must be primed by initial exposure to specific foreign substances (priming takes time)Know the 4 functions of Adaptive immune (specific defense) systems.

4 functions of Adaptive immune (specific defense) systems. are

1) specific, 2) systemic, and 3) have “memory”

Humoral Immunity: antibodies, produced by

lymphocytes, circulating freely in body fluids

Humoral Immunity, Bind temporarily to target cell

○ Temporarily inactive

○ Mark for destruction by phagocytes or complement

Cellular Immunity: Lymphocytes act against

target cell

Cellular Immunity: Lymphocytes act against target cell

● Directly – by

killing infected cells

Cellular Immunity: Lymphocytes act against target cell

Indirectly – by

releasing chemicals that enhance inflammatory response; or activating other lymphocytes or macrophages

what are Antigenic determinants (epitopes)

specific regions within an antigen to which antibodies or T-cell receptors can bind

Antigenic determinants are Composed of a unique sequence of amino acids or sugar moieties that

elicit an immune response and stimulate the production of antibodies or cellular immunity

Antigenic determinants (epitopes) are Essential in the body's defense against

pathogens and foreign substances, allowing the immune system to recognize and neutralize harmful agents

Only certain parts (antigenic determinants) of entire antigen are

immunogenic

Antibodies and lymphocyte receptors bind to them (Antigenic determinants) as

enzyme binds substrate

Most naturally occurring antigens have numerous antigenic determinants that Mobilize

several different lymphocyte populations

Most naturally occurring antigens have numerous antigenic determinants that Form different kinds of

antibodies against it

Antigenic determinants (epitopes), Large, chemically simple molecules (e.g. plastics) have

little or no immunogenicity

three types of cells in the adaptive immune system

B, T and APCs

Seeding Secondary Lymphoid Organs and Circulation, Immunocompetent B and T cells not yet exposed to antigen called

naive

Seeding Secondary Lymphoid Organs and Circulation are Exported from primary lymphoid organs (bone marrow and thymus) to "seed"

secondary lymphoid organs (lymph nodes, spleen, etc.)

– Increases chance of encounter with antigen

B lymphocytes (B-cells) have what kind of immunity

humoral immunity

B cells mature in

B cells mature in red bone marrow

B cells are Positively selected if successfully

make antigen receptors

B-cells that are self-reactive are

Eliminated by apoptosis (clonal deletion)

B cells Do not activate

naive T cells

B cells Present antigens to

helper T cell to assist own activation

T lymphocytes (T-cells) what kind of immunity

cell-mediated immunity

T lymphocytes (T-cells) mature in thymus under

negative and positive selection pressures ("tests")

T lymphocytes (T-cells), A very small fraction of cells

survive this process

Antigen-presenting cells (APCs) do not respond to

specific antigens & play essential auxiliary roles in immunity

5 steps for Lymphocyte Development, Maturation, and Activation

1. Origin (all originate in red bone marrow)

2. Maturation

3. Seeding secondary lymphoid organs and circulation

4. Antigen encounter and activation

5. Proliferation and differentiation

"Educated" as mature: "Educated" as mature:

B cells in bone marrow & T cells in thymus

"Educated" as mature: Immunocompetence

– lymphocyte can recognize one specific antigen by binding to it

Immunocompetence, B or T cells display unique receptor on surface when

achieve maturity – bind only one antigen

"Educated" as mature, Self-tolerance Lymphocytes unresponsive to

own antigens

positive and negative selection-a very small fraction of cells

survive this process

lymphocyte development, maturation, and activation

T cell education in the thymus diagram

Dendritic cells phagocytize pathogens &

enter lymphatics to present antigens to T cells in lymph node

Dendritic cells Found in various tissues throughout the body, including

the skin (Langerhans cells), mucosal surfaces, lymph nodes, and spleen

Dendritic cells are the Most effective

antigen presenter known

Dendritic cells are the Key link between

innate and adaptive immunity

Dendritic cells Can activate

naive T cells

Dendritic cells Present antigens to T cells to activate themselves into

voracious phagocytes that secrete bactericidal chemicals

Clonal selection of a B cell diagram

primary and secondary humoral responses

IgM, Pentamer

Pentamer (larger than others), first antibody released

IgM, Potent

Potent agglutinating agent

IgM, Readily fixes and activates

complement

IgA (secretory IgA), Monomer or

dimer, in mucus and other secretions

IgA (secretory IgA), Helps prevent entry

of pathogens

IgD, Monomer attached to

surface of B cells

IgD Functions as

B cell receptor

IgG, Monomer; 75–85% of antibodies

plasma

IgG, From secondary and

late primary responses

IgG, Crosses

placental barrier

IgE, Monomer active in some allergies and

parasitic infections

IgE, Causes mast cells and basophils to

release histamine

IgE, B cells can switch antibody classes but

retain antigen specificity

IgM at first, then IgG

Almost all secondary responses are IgG

IgM pentamer table 21.4

IgA (dimer) table 21.4

IgD (monomer) table 21.4

IgG (monomer) table 21.4

IgE (monomer) table 21.4