Lecture 21 Flashcards
When do immunological disorders occur?
when the immune system malfunctions
- overreacting
- underreacting
- attacking the body’s own tissues
What are hypersensitivities?
exaggerated immune responses to harmless substances
- antigenic response beyond normal
- occurs when sensitized by previous exposure to an antigen
- allergies
- asthma
What are autoimmune diseases?
immune system attacks self
- lupus
- rheumatoid arthritis
What are immunodeficiencies?
failure to protect against infections
- HIV/AIDS
- SCID
- IgA deficiency
What is the study of hypersensitivity reaction called?
immunopathology
What are the 4 types of hypersensitivity?
- anaphylactic
- cytotoxic
- immune complex
- delayed cell-mediated
What is anaphylactic reaction?
- immediate and occurs minutes after a person sensitized to an antigen is re-exposed to that antigen
- antigens combine with IgE antibodies
- IgE attaches to mast cells and basophils, which undergo degranulation to release mediators
What is the function of histamine?
increases permeability of blood capillaries
What is the function of leukotrienes?
cause prolonged contraction of smooth muscles
What is the function of prostaglandins?
affect smooth muscle and increase mucus secretion
What is systemic anaphylaxis? What is it treated with?
anaphylactic shock
- results when an individual sensitized to an antigen is exposed to it again
- may result in circulatory collapse and death
- treated with epinephrine
What is localized anaphylaxis? Give examples.
- usually associated with ingested or inhaled antigens
- symptoms depend on route of entry
- hives, fever, asthma
What is desensitization therapy?
increasing dosages of antigen injected beneath the skin
- produces IgG, which act as blocking antibodies to intercept and neutralize antigens
What is cytotoxic reaction?
- activation of complement by the combination of IgG or IgM antibodies with an antigenic cell (macrophages causes cell lysis or damage)
- ABO blood group system (antibodies form against certain carbohydrates antigens on RBCs
= type O RBCs have no antigens - Rh blood group system
- drug-induced cytotoxic reactions
What is the Rh blood group system?
- Rh factor antigen found on RBCs of 85% of the population
- Rh+ blood to a Rh- recipient can stimulate anti-Rh antibodies in the recipient
What is HDNB?
hemolytic disease of the newborn
- Rh- mother with an Rh+ fetus causes the mother to produce anti-Rh antibodies
- second Rh+ fetus will receive anti-Rh antibodies, damaging fetal RBCs
What is thrombocytopenic purpura?
- platelets combine with drugs, forming a complex that is antigenic
- antibody and complement destroy platelets
What is agranulocytosis?
drug-induced immune destruction of granulocytes
What is hemolytic anemia?
drug-induced immune destruction of RBCs
How do type III reactions work?
1) immune complexes are deposited in wall of blood vessel
2) presence of immune complexes activates complement and attracts inflammatory cells
3) enzymes released from neutrophils cause damage to endothelial cells of basement membrane
When can serum sickness occur?
injection of foreign serum
- swelling and inflammation
What is arthus reaction?
rare side effect of toxoid containing vaccines
- occurs in glomeruli and other vessel walls due to complement activation
When do antibodies form?
against soluble antigens in the serum
What is the overall purpose of the immune complex?
lodges in the basement membranes beneath the cells
- activates complement, causing inflammation
What is type IV reactions?
delayed cell-mediated
What is delayed hypersensitivity?
cell-mediated immune responses caused by T cells
What happens to antigens in delayed cell-mediated?
phagocytized and presented to receptors on T cells, causing sensitization
What happens to reexposure to antigens in delayed cell-mediated reactions?
causes memory cells to releases destructive cytokines
What is allergic contact dermatitis?
- haptens combine with proteins in the skin, producing an immune response
- allergic response to poison ivy, cosmetics, metals, latex
What is the time limit for each type of reaction?
type 1: less than 30 minutes
type 2: 5-12 hours
type 3: 3-8 hours
type 4: 24-48 hours
What is autoimmunity?
loss of self-tolerance
- ability to discriminate self from nonself
What type of reaction is multiple sclerosis?
typer 2 cytotoxic autoimmune reactions
What happens to the nerves during multiple sclerosis?
- autoantibodies, t cells, macrophages attack myelin sheath of nerves
- compromises nerve impulse transduction
What are symptoms for multiple sclerosis?
fatigue and weakness to severe paralysis
What type of autoimmune reaction is graves’ disease?
type 3 immune complex autoimmune reactions
What causes graves’ disease?
abnormal antibodies in the thyroid produce excessive amounts of hormones
- hyperthyroidism
What type of autoimmune reaction is myasthenia gravis?
type 3 immune complex autoimmune reactions
What causes myasthenia gravis?
antibodies coat acetylcholine receptors
- muscles fail to receive nerve signals
What autoimmune reaction is systemic lupus erythematosus?
type 3 immune complex autoimmune reactions
What is systemic lupus erythematosus?
butterfly rash
- immune complexes form in the kidney glomeruli
What autoimmune reaction is rheumatoid arthritis?
type 3 immune complex autoimmune reactions
What is rheumatoid arthritis?
immune complexes form in the joints
What autoimmune reaction is insulin-dependent diabetes mellitus?
type 4 cell-mediated autoimmune reactions
What is insulin-dependent diabetes mellitus?
t cell destruction of insulin-secreting cells
What type of autoimmune reaction is psoriasis and psoriatic arthritis?
type 4 cell-mediated autoimmune reactions
What is psoiasis?
autoimmune disorders of the skin
What are some autoimmune reactions to transplantation?
- histocompatibility antigens: self antigens on cell surfaces
- major histocompatibility complex: genes encoding histocompatibility antigens
- human leukocyte antigen complex: MHC genes in humans
= certain HLAs are related to increased susceptibility to specific diseases
How does human leukocyte antigen complex work?
- identifies and compares HLAs
- donor and recipient must be matched by tissue typing
- uses standardized antisera or monoclonal antibodies specific for HLAs
What are privileged sites and privileged tissues?
don’t cause immune response
- cornea transplants
- heart valve transplants
Why do we use privileged sites?
transplants may be attacked by t cells, macrophages, and complement fixing antibodies
What are stem cells?
master cells capable of renewing themselves and differentiating into organ-specific specialized cells
What are embryonic stem cells?
- harvested from blastocysts
- used to regenerate tissues and organs
- can generate all types of cells (pluripotent)
What are adult stem cells?
- stem cells in adult tissues that have differentiated
- can become induced pluripotent stem cells by introducing genes
What are bone marrow transplants known as?
hematopoietic stem cell transplants
What is the goal of bone marrow transplants?
enables recipient to produce healthy blood cells
What causes graft-versus-host disease?
transplanted bone marrow that contains immunocompetent cells
What is autograft?
use of one’s own tissue
What is isograft?
use of identical twin’s tissue
What is allografts?
use of tissue from another person
What is xenotransplantation product?
use of nonhuman tissue
- must overcome hyperacute rejection (response to nonhuman antigens)
How can immunosuppression work to prevent transplant rejection?
- prevents a cell-mediated immune response to transplanted tissues
- cyclosporine and tacrolimus suppress IL-2, disrupting cytotoxic T cells
- sirolimus inhibits cellular and humoral immunity
- mycophenolate inhibits the proliferation of T cells and B cells
What blocks IL-2?
basiliximab
- chimeric monoclonal antibody
How are cancer cells removed?
immune surveillance
What lyses cancer cells?
- CTLs (activated Tc cells)
- macrophages
What are limitations to the immune system when fighting cancer?
- no antigenic epitope for the immune system to target
- tumor cells reproduce too rapidly
- tumor becomes vascularized and invisible to the immune system
How does immunotherapy for cancer work?
- endotoxins from bacteria stimulate TNF that interferes with the blood supply of cancers
- vaccines used for prophylaxis (cervical, anal, throat cancer [HPV], liver cancer)
- monoclonal antibodies (herceptin for breast cancer, immunotoxin combines a Mab with a toxic agent)
What is congenital immunodeficiencies?
due to defective or missing genes
What is selective IgA deficiency?
- mostly asymptomatic
- recurrent respiratory or GI infections
- increased risk of autoimmune diseases or allergies
- laboratory diagnosis low or absent serum, with normal levels of other immunoglobulins
What is acquired immunodeficiencies?
develop during an individual’s life
- due to drugs, cancers, infection
How do acquired immunodeficiencies occur due to drugs?
- corticosteroids
= suppresses immune responses by reducing inflammation and impairing t-cell function
How do acquired immunodeficiencies occur due to cancers?
- leukemias and lymphomas
= cancers of the blood and lymphatic systems impair the production and function of white blood cells
How do acquired immunodeficiencies occur due to infections?
- HIV/AIDS
= targets CD4+ t-cells
