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
