Unti 2 - Lecture 10 Adaptive Immunity Flashcards
What are some comparisons of the innate and adaptive immunity?
What are some characteristics of Adaptive (specfic) Immunity?
- Includes B and T lymphocytes
—B lymphocytes are born and mature in the bone marrow.
—-T lymphocytes are born in the bone marrow and mature in the thymus gland.
- Lymphatic system supplies lymphocytes to the bloodstream.
- Lymphocytes congregate in the lymph nodes and exit through the outgoing lymph vessels.
—–Interaction with innate immune cells (dendritic cells)
What is the Lymphatic System?
Lymphatic System
- Part of the circulatory system
- Network of conduits called lymphatic vessels
- Carries a clear fluid called lymph which contains white blood cells
What is the Primary Lymphoid Organs?
- Sites of lymphocyte maturation
- Bone marrow and thymus
What are Secondary Lymphoid Organs?
- Sites of lymphocyte activation
- Lymph nodes, tonsils, spleen and Perer’s patches
What are lymph nodes?
- Organized lymphoid tissue distributed widely throughout the body
- 500-600 in humans
- Act as “filters” or “traps” for foreign particles
- Dendritic cells take up antigens and activate lymphocytes
- Become inflamed or enlarged during infection
- Outer cortex: B cells and T cells
- Inner medulla: macrophages, B cells, and plasma cells
What is involved in the spleen?
- Located in the left abdominal cavity
- Specializes in filtering blood and trapping blood-borne antigens/pathogens
- Dendritic cells take up antigens and activate lymphocytes
- Become inflamed or enlarged during infection
- Red pulp: Destruction/removal of old or defective red blood cells.
- White pulp: populated by T and cells
- Germinal centers: site where mature B cells rapidly divide, differentiate, and undergo somatic hypermutation
A cell of the adaptive immune system such as
B cell.
What is a B cell?
A “B” cell is an antigen binding receptor (antibody)
- Primary function is to make antibodies (also called immunoglobulin)
- Surface B cell receptor is identical to the antibody secreted
- Recognize antigens in their native form (soluble antigens)
- Activation and function “helped” by CD4+ T cells
With antibody production what is the Humoral Response?
- Humoral= “arising from the body”
- Serum= unclotted portion of blood
—-Complement and antibodies
•Antibody half-life 7-23 days
•Also found in mucosal secretions (IgA)
What are antibodies?
- Recognize a unique part of a foreign invading microbe called an antigen
- Y-shaped protein
- 2 identical heavy chains (VH)
- 2 identical light chains (VL)
- Linked via disulfide bridges
- Two antigen binding sites (Fab regions)
- Fc region mediates antibody function
What is the Antibody Structure?
What is the affinity?
Affinity: Strength which an antibody binds to a antigen
What are Antibody Isotypes?
- Five major classes of antibody:
- IgM
- IgG
- IgA
- IgD
- IgE
- Differ in heavy chain Fc region structure
- Different structural and functional properties
What is Immunnoblobulin (IgG)?
- Makes up ~80% of serum antibodies
- Monomer with 2 antigen-binding sites
- Fc portion:
Activates classical complement pathway
Enhances phagocytosis
Bind to NK cells to mediate cytotoxicity
Only class able to cross the placenta and enter fetal circulation
What is Immunoglobulin M (IgM)?
- Makes up ~13% of serum antibodies
- Half-life of about 5 days
- Low affinity
- Pentamer with 10 antigen-binding sites
Joining (J) chain needed for pentameric form
- First class produced in primary response to an antigen/pathogen
- Monomeric form expressed on surface of B cells (BCR)
- Fc portion:
Most efficient class for activating the classical complement pathway
What is Immunoglobulin A (IgA)?
- Found mainly in body secretions
Saliva, tears, milk
- Dimer with 4 antigen-binding sites
- Secretory component critical for transport into secretions and protection from digestive enzymes
- Protects mucosal surfaces by blocking viral attachment
Descibe T-Cell Mediated Immunity
- T cells recognize “cells” that contain foreign antigens (e.g., virally infected cells).
- B-cells and T-cells recognize fundamentally different viral structures.
B-cells recognize whole protein antigens.
T-cells recognize processed short viral peptides.
- At least two defined populations of T cells
Cytotoxic T cells (TC)
T helper cells (TH)
- Express a unique T cell receptor (almost unlimited specificities)
- Recognize antigens displayed on the surface of antigen-presenting cells
- Primary functions are cytokine secretion (CD4) and cytotoxicity (CD8)
