Chapter 7: Adaptive Immunity Flashcards
Humoral and Cell-Mediated Immunity
The cellular and humoral responses are not independent Humoral immunity -"fluid" immunity -circulating antibody Cell-mediated immunity -T cell differentiation
Adaptive Immunity
Works together with innate immunity, aka inflammation
Specificity
-each T or B cell recognizes only one antigen, but together a group of T and B cells recognize a host or foreign antigens
Memory
-confers long-term protection
Types of Immunity
Natural immunity: natural exposure to antigens and antibodies are produced
Artificial immunity
-active immunity:vaccinations
-passive immunity:preformed antibodies or t lymphocytes are transferred from a donor to the recipient
Active vs Passive Immunity
Active immunity: antibodies or T cells produced after either natural exposure to an antigen or after immunization
Passive immunity: preformed antibodies or T lymphocytes are transferred from a donor to recipient
Antigen
A molecule that can react with (or be recognized by) the immune system
Recognized as non-self
Pathogens (viruses, bacteria, fungi, etc.), bee venom, pollen, foods, tissue, blood products
Antigen Recognition
Antigen is directly recognized by circulating antibody, antigen receptors on B cells(BCR) and T lymphocytes(TCR)
For recognition by T cells antigens are presented by antigen presenting cells via processing and completing with major histocompatibility complexes(MHC)
MHC I: for presenting intracellular antigens. Antigen complexes with MHC I in endoplasmic reticulum and then complex is inserted into the plasma membrane
MHC II: for presenting antigens from extracellular sources. Antigen combines with MHC II in intracellular vesicles and is transported to cell surface for presentation
CD I: antigen is processed in vesicles and presented at cell surface. Antigen is lipid based
Transplantation
Cells in transplanted tissue from one individual have a different set of MHC surface antigens than those of recipient
Thus recipient can mount an immune response against foreign MHC molecules
Also known as human leukocyte antigen (HLAs)
T and B Lymphocytes
General processes of maturation:
-lymphocytes arise from hemopoietic cells in red bone marrow
-T cells mature in thymus, and B cells in the bone marrow
Immuno competence
Self tolerance
Immunocompetent T and B cells go to secondary lymphoid organs(spleen for T cells, lymph nodes for B cells). Clonal expansion of cells that recognize presented antigens
B cells produce antibodies
Antibodies aka immunoglobulins
Protein in nature
Part of the adaptive immune response that interacts with antigen
Classes of antibody: IgG, IgA, IgM, IgE and IgD
(Characterized by antigenic, structural and functional differences)
Antibody structure
Polypeptide chains(4) -light chains(2) and heavy chains(2) -held in a Y shape and held together by disulphide bonds Variable region -constitutes the antigen binding site -specificity Constant region -remainder of heavy and light chains -determines the class of antibodies
Immunoglobulin M(IgM)
Largest or immunoglobulins
Pentamer stabilized by j-chain
First antibody produced during primary response to an antigen
Large, doesn’t cross from blood to tissues
Immunoglobulin G(IgG)
Most abundant class (80%-85%)
Transported across placenta
Four classes IgG1,IgG2,IgG3 and IgG4
React with most types of antigens
Immunoglobulin A(IgA)
2 classes
-IgA1 molecules:predominantly in the blood
-IgA2 molecules:predominantly in normal body secretions
Protects mucosal membranes especially digestive and respiratory tracts
Immunoglobulin E(IgE)
Least concentrated of the immunoglobulin classes in the circulation
Mediator of many common allergic responses
-Fc portions of IgEs are bound mast cells
Defender against parasites
Immunoglobulin D(IgD)
Limited information on IgD function
Low concentration in blood
Located primarily on the surface of developing B lymphocytes
Function as one type of B cell antigen receptor
Primary Response
Initial exposure
Latent period or lag phase (B cell differentiation is occurring)
After 5 to 7 days, an IgM antibody for a specific antigen is detected
An IgG response equal it slightly less follows the IgM response
Secondary response
More rapid
Larger amounts of antibody are produced
Rapidity is due to the presence of memory cells that do not have to differentiate
IgM is produced in similar quantities to the primary response but IgG is produced in considerably greater
T cells
Generate clinal diversity in thymus
Produce Helper T cells and Cytotoxic T cells
These cells migrate to spleen and are presented with antigen and then differentiate into mature T cell form
Helper T Lymphocytes
Subsets
- Th1 cells provide help in developing cell-mediated immunity
- Th2 cells provide help in developing humoral immunity
- Th17 cells promote inflammatory response by activating neutrophils and macrophages
- t regulating cells limit immune response to prevent autoimmune diseases
Cytotoxic T lymphocytes
Destroy cancer cells or cells infected with virus via apoptosis
Cells adhere to target cells through antigen presentation in association with MHC I
