Chapter 19 Part 3
Response of reduction of NK cells
Immunological surveillance is compromised -Cancer has a higher risk
IgA
In glandular secretions such as mucus, tears, saliva, and semen
T cell activation by infected cells
Inactive T cells have receptors that recognize either Class I or Class II MHC proteins when bound to specific antigen It will only detect it if the MHC protein contains the antigen that that T cell is programmed to detect --This is called antigen recognition
Allergies
Inappropriate (or excessive) immune responses to antigens (allergens) Sensitization and activation of B cells to allergens leads to a production of large quantities of IgE
Gaft rejection
Recipient Cytotoxic T cells become activated and attack MHC proteins of donated material Reduction in immune response sensitivity (immunosuppression) by drugs can increase transplant success Ex: Cyclosporin A inhibits helper T cells
Primary response of antibodies
Response to initial antigen exposure: delayed due to time to activate specific B cells Antibody titer (level of antibody activity) peaks 1-2 weeks after initial response
Examples of autoimmune disorders
Rheumatoid arthritis (attack on connective tissue around joints) Insulin-dependent (type I) diabetes mellitus (attack on pancreas) Multiple sclerosis (attack of myelin)
Antibodies
Small soluble proteins that bind to specific antigens; they may inactivate the antigen or trigger another defensive process
Full activation of B cells occurs
When activated helper T binds to sensitized B cell antigen-Class II MHC complex
Specific and non-specific defenses:
Work together to defeat pathogens
T cell activation and cell division
Three CD8 cells produced 1. Cytotoxic T cells (most) 2. Memory T cells 3. Suppressor T cells
Memory T cell
Upon 2nd exposure to antigen, become cytotoxic T cells
IgG
(80% of all antibodies) against many viruses, bacteria, and bacterial toxins
Steps of CD8 recognition
1. Antigen recognition 2. Costimulation 3. T cell activition and cell division
Result of allergies
1. Localized inflammation, pain, itching -Ex: hypersensitivity reaction of allergic rhinitis --Ex: hay fever and other pollens 2. Systemic (allergen in blood stream, symptoms are widespread -Ex: anaphylaxes (circulating allergens causing widespread vasodilation through mast cell activation
Class II MHC protein activation
1. Phagocytic APCs engulf the extracellular pathogens 2. Lysosomal action produces antigenic fragments 3. ER produces Class II MHC proteins 4. Antigenic fragments are bound to class II MHC proteins 5. Antigenic fragments are displayed by class II MHC proteins on the plasma membrane
Immunodeficiency diseases result form
1. Problems with lymphoid organ and tissue development 2. An infection with a virus that depresses immune function -example: acquired immune deficiency syndrome caused by human immunodeficiency virus (HIV) that infects CD4 cells 3. Treatment or exposure to immunosuppressive agents like radiation or drugs
Autoimmune disorders
Activated B cells B cells make antibodies against "self-" antigens on body cell tissues=autoantibodies -likely to arise from body cell antigens being too similar to specific foreign antigens
Activation of complement
After antigen binding, complement also can bind to the antibody accelerating the complement cascade
IgM
Anti-A and Anti-B are examples
Neutralization
Antibodies bind viruses and bacterial toxins Prevents them from affecting body cells
Overview of MHC activation
Antigen presentation by Class I MHC proteins is triggered by viral or bacterial infection of body cell Infection leads to abnormal peptides Abnormal peptides are incorporated into Class I proteins as they are synthesized in the ER After export to the golgi, MHC proteins reach plasma's membrane within transport vesicles The abnormal peptides are displayed by class I MHC proteins on plasma membrane
IgE
Attach to basophils and mast cells causing release of histamines
Attraction of phagocytes attached to antibodies
Attract eosinophils, neutrophils, and macrophages
Stimulation of inflammation
Basophil and mast cells stimulation to release histamine
Cytotoxic T Cells
Destroys infected and abnormal cells Target cells must have specific Class MHC proteins -Release of perforins and activation of target cells self-destruction genes for death (apoptosis)
Classes of antibodies
Differences in constant segments 1. IgG 2. IgE 3. IgD 4. IgM 5. IgA *all formed in human milk, but IgA is most abundant
Response of T cells becoming less responsive with age
Fewer cytotoxic T cells
Constant segment of Antibodies
Form the base
Secondary response of antibodies
From memory B cells to specific antigen Antibody titers increase more rapidly (and each higher concentration especially IgGs)
Major histocompatibility complex (MHC) proteins
Genetically determined membrane glycoproteins present on all cells Foreign antigens attach to these MHC proteins and appear on cell surface T cells bind antigens MHC complex and become activated
Class II MHC proteins
Only in membranes of antigen-presenting cell (APC) ex: macrophages Create complex with phagocytized pathogens
Triggering an immune response
Involves Major Histocompatibility Complex (MHC) proteins
Suppressor T cell
Limit response of other T cells and B cells
Agglutination
Linking of multiple pathogens by antibodies creating an immune complex
B cell activation
Must bind a specific antigen Antigens brought into the cell through endocytosis/phagocytosis, and then placed on the surface of a cell bound to Class II MHC proteins This process is sensitization or the preparation to undergo B cell activation
Primary antibody actions
Neutralization Activation of complement Stimulation of inflammation Agglutination Attraction of phagocytes
CD4 markers
On CD4 T cells Respond to class II MHC proteins
CD8 markers
On CD8 T cells Respond to class I MHC proteins
Costimulation
Physical or chemical stimulation of T cell in addition to the Class I MHC molecule
Activated B cells produce
Plasma cells (activated B cells: produce antibodies) Memory B cells (inactive until 2nd exposure to antigen)
IgD
Plays a role in B cell sensitization
Variable segment of antibodies
Possess antigen binding sites Differences in amino acid sequences produce variability needed for different antibodies Ex: binding a bacterium
Cause of less T cells with age
Possibly due to thymus atrophe
Class I MHC proteins
Present on all cells and create a complex when cell is infected with bacteria or viruses
Age-related reductions in immune activity
T cells become less responsive B cells respond less due to less helper T cells (vaccinations highly recommended for elderly individuals) NK cells reduced
CD (Cluster Differentiation) markers
The membrane proteins involved in antigen recognition CD8 markers CD4 markers