Chapter 8 Flashcards
(32 cards)
Adaptive Immunity
The third line of defense in the human body
- Once barriers (1st line) and inflammation (2nd line), the adaptive immune response is called into action
- Augments the initial defenses against infection and provides long-term security against reinfection
Humoral Immunity
Is the aspect of the immune system that synthesizes immunoglobulins
Humoral = Antibodies
Cellular Immunity
- Does not synthesize antibodies
- Driven by T cells
- Works by the release of cytokines and phagocytes
Active vs. Passive Immunity
Active immunity is produced by an individual either after natural exposure to an antigen or after immunization, whereas passive immunity does not involve the host’s immune response at all
What are antigens?
A molecule that can react with binding sites on antibodies or antigen receptors on B and T cells
- Most, but not all, antigens are also immunogens
What are antibodies?
A serum glycoprotein produced by plasma cells in response to a challenge by an immunogen
What are the function of antibodies?
IgG
- The most abundant immunoglobulin (76%)
- Located in plasma, interstitial fluid
- Only immunoglobulin that crosses placenta
- Responsible for secondary immune response
IgA
- Accounts for 15% of immunoglobulins
- Found in body secretions, tears, saliva, breast milk, colostrum
- Lines mucous membranes and protects body surfaces
IgM
- Accounts for 8% of immunoglobulins
- Largest immunoglobulin
- First antibody produced during the initial, or primary, response to antigen
- Usually synthesized early in neonatal life, but may be increased as a response to infection in utero
IgE
- Lowest amount of immunoglobulin
- Functions as a mediator of many common allergic responses and in the defense of parasitic infections
IgD
- 1% of immunoglobulins
- Functions as an antigen receptor on the surface of early B lymphocytes
B-Cell Receptors
is a complex of antibody bound to the cell surface and other molecules involved in intracellular signaling
-Its role is to recognize antigen and communicate that information to the cell’s nucleus
T-Cell Receptors
is composed of an antibody-like transmembrane protein and a group of accessory proteins that are involved in intracellular signaling
- Similar to the BCR, the TCR is responsible for recognition and binding to the antigen, whereas the accessory proteins are responsible for the intracellular signaling necessary for activation and differentiation of the T cell
Transplantation
- Cells in transplanted tissue or organs from one individual will have a different set of MHC (major histocompatibility complex) surface antigens than those of the recipient; therefore, the recipient can mount an immune response against the foreign MHC antigens, resulting in rejection of transplanted tissue
- The more similar tow individuals are in their HLA (human leukocyte antigen) tissue type, the more likely a transplant from one to the other will be successful
CD1
- A type of antigen-presenting molecule
- Have very low genetic polymorphism a structure similar to MHC
- Found in cells of the thymus
- Appear to specialize in presenting lipid antigens contained in lipoproteins, glycolipids, and other molecules
- Very important in infections with Mycobacterium (TB and leprosy) which have a very large amount of lipid in their cell membranes
Cytokines
- A large number of cytokines are secreted by APCs and lymphocytes and provide both positive and negative regulation of the immune response
- Can cause a lymphocyte to proliferate and differentiate
- The participation of cytokines is essential to the development of an adequate immune response, and in general the precise combination of cytokines influences the ultimate response of a given cell
Clonal Diversity and Selection
- During generation of clonal diversity, a large population of T cells and B cells is produced before birth
- Clonal selection is the process by which antigen selects lymphocytes with complementary TCRs or BCRs and induces an immune response with the production of specific antibody or cytotoxic T cells, or both
B Cells
Lymphoid stem cells enter bone marrow and differentiate into B lymphocytes
- B cells can differentiate into plasma cells which produce antibodies (immunoglobulins)
- Can differentiate into long-lived memory cells
T Cells
Lymphoid stem cells that migrate from bone marrow to the thymus and differentiate into T lymphocytes
- T cells make up 70-80% of the circulating lymphocytes and are primarily responsible for immunity to intracellular viruses, tumor cells, and fungi
- T cells live from a few months to the life span of an individual and account for long-term immunity
Secondary Lymphoid Organs
- Spleen
- Lymph nodes
- Adenoids
- Tonsils
-Peyer patches
Antigen Processing
The process by which phase 2 of adaptive immunity is achieved
- the process requires the cooperation among a variety of cells in the secondary lymphoid organs; most antigens need to be processed by phagocytic cells, primarily dendritic cells, that also present the processed antigen on their surfaces and present the antigen to lymphocytes
T-Helper Lymphocytes
- Most immune responses require T-helper cells (Th cells)
- Precursor Th cells interact with APCs through the TCR-CD4 complex, a variety of adhesion molecules, and cytokines, especially IL-1, and develop into either Th1 or Th2 subsets
- Th1 cells help activate macrophages and cytotoxic T cells
- Th2 cells help activate B cells
Primary and Secondary Immune Responses
- The primary immune response is the first exposure to the antigen
- The secondary response has a much higher proportion of IgG relative to IgM
- The secondary response is much more rapid than the primary response because of the presence of memory cells in the secondary phase