Lecture 26- Adaptive Immunity, Antibody Responses

Adaptive Immunity

specific, inducible, acquired upon exposure to pathogen, makes antibodies, antigen processing and presentation, and cell mediated cytotoxicity

Adaptive Immunity Function

body’s ability to recognize and defend itself against distinct invaders (pathogens and irregular host cells) and their products

5 Main Attributes of Adaptive Immunity

1) specificity

2) inducibility

3) clonability

4) unresponsiveness to self

5) memory

Specificity of Adaptive Immunity

acts only against specific molecular shapes, antigens, from individual pathogens

Inducibility of Adaptive Immunity

only recognition of that specific antigen from a pathogen will initiate the response

Clonality of Adaptive Immunity

when induced, many generations of cells with identical response capabilities to a specific pathogen will be generated

Unresponsiveness to Self, Adaptive Immunity

self vs non self-recognition, response is only to the pathogen and not the host

Memory, Adaptive Immunity

once an adaption response to pathogen is initiated, the antigen will be remembered for future encounters

Blood and lymph

the conduits for adaptive immune communication between tissues

Lymphatic System Composition

1) composed of lymphatic vessels and lymphoid cells, tissues, and organs

2) lymphoid tissues contain the vast majority of the total immune cells in body

Lymphatic System Function

screen the tissues of body for foreign molecules

Main Organs of Lymphatic System

lymph nodes, bone marrow, spleen, thymus, tonsils, intestines, GALT (gut associated lymphoid tissue)

Lymphatic Vessels

one way system that conducts lymph from tissues and returns it to the circulatory system

Lymph

liquid with similar composition to blood plasma, arises from fluid leakes from BVs into surrounding tissues

Components of Blood

1) plasma- liquid component (55%) containing water, proteins salts, and hormones

2) RBCs- erythrocytes, carry oxygen using hemoglobin

3) WBCs- leukocytes, defend against infection

4) platelets- responsible for clotting

Adaptive Immunity Cells

B (antibody production) and T (cell mediated responses) cells from Lymphoid Stem Cells

What are the 2 Lymphocytes

1) B cells

2) T cells

B Cells Maturation

cells develop and mature in the bone marrow

T Cell Maturation

in the thymus

B cell Involvement

in antibody mediated functions of the adaptive immune system

T cell involvement

in cell mediated functions of the adaptive immune system

Antibody Response

humoral response, B cells and antibodies, the antibodies are secreted by B cells specific to individual antigens

5 Different Types of antibodies in the Body

1) IgG

2) IgM

3) IgA

4) IgD

5) IgE

IgG

monomer, involved with complement activation, virus and toxin inactivation, and opsonization

IgM

pentamer, complement activation (1000x better than IgG), involved with adaptive response

IgA

dimer, involved with mucosal immunity (airways, intestines, newborn passive immunity in breastmilk)

IgD

monomer, involved with mucosal homeostasis, not well understood

IgE

monomer, inflammation, controlling parasites

Key Antibody Structural Components

1) antigen binding sites for pathogen recognition

2) Effector with Stem and Fc, communicate with immune system

3) Fav= fragment, antigen binding

4) Fc= fragment, crystallizable

IgG Features

major class of antibody in the bloodstream, 80% of Ab in blood/serum

IgA Features

found in the highest concentration in breast milk, although IgG and IgM are also found in breast milk and colostrum, most abundant in intestine, but IgG and IgM also present

IgM Features

largest of all antibodies, contains 10 antigen binding sites per molecule allowing high avidity binding even through lower amounts present than IgA and IgG in body

Antigen

substance that interacts with specific antibody

Immunogen

antigen that elicits the immune response

Epitope

antigenic determinant, part of the antigen recognized by antibody binding site

IgM and IgG Antibody Response

major antibody responses to pathogens, and their levels are indicative of acute vs chronic infection

IgM and IgG during Initial Antigen Exposure

primary response, IgM levels rise rapidly, IgG is slower, IgM and IgG total response is similar

IgM and IgG during Secondary Antigen Exposure

lag period is reduced, especially for IgG, IgG levels maintained for longer duration, IgG amounts greater, IgM levels comparable to initial response

B Cell Antigen Recognition

1) recognition of diverse epitopes, many different molecular patterns can be recognized by B cells during adaptive immunity, TLRs from innate immunity recognize 20-50 distinct pathogen associated molecular patterns (PAMPs)

2) long term memory, generation of memory cells that can circulate within the body for many years

3) sustained response can be weeks to months

B Lymphocytes (B Cells) and Antibodies

1) Each B lymphocytes has multiple copied of BCR

2) each B cell generates a single BCR

3) 2 variable regions of the BCR form antigen binding sites

4) each BCR recognizes only one epitope

5) entire repertoire of BCRs expressed by all B cells in an individual is capable of recognizing millions of different epitopes at any given time

B Cell Receptor Mediate B Cell antigen Recognition

1) BCR binds the antigen

2) antibody secretion

3) antigen binding

B cells Secreting Antibodies, 6 Steps

they are called plasma cells

1) B cell binds antigen

2) B cell activation

3) antibody producing B cell, plasma cell

4) antibody secretion

5) antibodies released into the body

6) antibodies neutralize virus

Antibodies and Pathogen Clearance

1) neutralization

2) agglutination

3) antibody dependent cell mediated cytotoxicity (ADCC)

4) opsonization

B Cell Activation from T cells

T cells secrete cytokines which can activate B cells