Chapter 18: Immune Disorders Flashcards
Immunological disorder:
is a condition that results from an inappropriate or inadequate immune response
Hypersensitivity
“Allergy”, the immune system reacts in an exaggerated or inappropriate way to a foreign substance that is harmless
Are allergies due to immunological responses?
No
What determines the type of hypersensitivity?
The component of immune response that is involved and how quickly the reaction develops
Immediate hypersensitivity
Type 1, Anaphylaxis resulting from a prior exposure to a foreign substance called an allergen
Allergen
an antigen that evokes a hypersensitivity response
Cytotoxic hypersensitivity
Type 2, elicited by antigens on cells, especially RBCs that the immune sees as foreign (occurs when patient receives wrong blood type)
Immune complete hypersensitivity
Type 3, elicited by antigens in vaccines in microorganisms or on a persona own cell, large antibody-antigen complexes formed, can cause damage within hours
Cell mediated or delayed hypersensitivity
Type 4, triggered by exposure to foreign substances from the environment [poison ivy], transplanted tissue, can cause extensive tissue damage
Autoimmune disorders
(1) Represent a form of hypersensitivity in which the body’s immune system responds to its own tissues as if it were foreign (2) Antibodies or T cells attack self-antigens
Immunodeficiency
The immune system responds in adequately to an antigen due to inborn or acquired defects
Primary immunodeficiency
Genetic or developmental defects in which the person lacks T cells or B cells or has defective ones
Secondary immunodeficiency
Results from damage of T cells or B cells after they have developed normally (Leukemia, Burkitts lymphoma), Happens after birth
Type 2 Hypersensitivity
(1) Blood trasnfusions (2) Specific antibodies react with cell surface antigens interpreted as foreign by the immune system (3) Leading to phagocytosis, killer cell activity or complement mediated cell lysis
Hemolytic Disease of the newborn
Erythroblastosis fetalis, If antibodies are made against baby who is Rh +, complement is activated and RBC’s are destroyed leading to this hemolytic disease
Type 3 Hypersensitivity
(1) When humans get antibodies from another source that is not human and it is seen as foreign and we make antibodies to those antibodies (2) Results in too many immune antigen-antibody complexes formed in our body which is not good and it disrupts tissue and can even cause blot clots leading to necrotic tissue
Mechanisms of immune complex disorders
(1) Initiated after sensitization (2) Specific IgG antibodies combine with antigen in blood to form immune complex to activate complement (3) Occurs when phagocytes fail to bind to the complexes and the complexes then travel to the blood to the rest of the body
Hydrolytic enzymes
Tissue damaging enzyme caused by phagocytes attracted to histamine released areas
Serum sickness: Immune complex disorder
(1) Large doses of antitoxin sera used to immunize people passively (2) People with serum sickness usually have fever, enlarged lymph nodes, decreased numbers of circulating leukocytes and swelling at injection site
Arthus reaction: Immune complex disorder
(1) A local reaction seen in the skin after subcutaneous or intra-dermal injection of an antigenic substance (2) Occurs in those who already have large amounts of antibodies (IgG) (3) Leads to edema, swelling, blood clots, cell death (4) “Pigeon fanciers lung”
Type 4 hypersensitivity
(1) Delayed hypersensitivity, takes more than 12 hrs to develop (2) APC presents antigen fragments and sensitizes TH1 cell (3) TH1 helps macrophages by secreting cytokines which encourage macrophage to work harder and speed up reaction to rid pathogen (4) More macrophages come to the site (5) TB skin test is a type 4
Which hypersensitivity types involve antibodies? and which one doesn’t contain antibodies (what does mediator does it use instead?)
Type 1,2,3 use antibodies, Type 4 uses T cells and cell mediated TH1
Main mediator and helping mediators in type 1 hypersensitivity
Main: IgE
Other: Mast cells, basophils, histamine, prostaglandins, leukotrienes
Main mediator and helping mediators in type 2 hypersensitivity
Main: IgG and IgM
Other: complement
Main mediator and helping mediators in type 3 hypersensitivity
Main: IgG, IgM
Other: Complement, inflammatory factors, eosinophils, neutrophils
Main mediator and helping mediators in type 4 hypersensitivity
Main: T cells (mainly TH or TDH)
Other: Lymphokines and macrophages
Sensitized Th cells release what?
Cytokine, Y interferon and migrating inhibiting factor
How do cells become antigenic?
The become antigenic because they bind to normal proteins on Langerhan cells of the epidermis which show to be antigen presenting cells due to their MHCII and then noticeable reactions occur
Gamma interferons stimulate what?
Macrophages
Migrating Inhibiting Factor (MIF) prevents what?
Migration of macrophages so they remain localized (leads to eczema, swelling and granulomatous lesions)
Contact dermatitis: cell mediated disorder
occurs in sensitized individuals on subsequent or second exposure to allergens such as oil from poison ivy, rubber, metals, dyes, soaps, cosmetics
Tuberculin Hypersensitivity: cell mediated disorder
Occurs in sensitized individuals when they are exposed to tuberculin (an antigen lipoprotein from the tubercle bacillus), can cause leprosy and leishmaniasis, [Antigen activates Th cells which then release cytokines causing large numbers of lymphocytes, monocytes and macrophages to infiltrate the dermis]
Granulomatous hypersensitivity: cell mediated disorder
(1) Most serious cell mediated hypersensitivities (2) occurs when macrophages have engulfed pathogens but failed to kill them, (3) pathogen survives in macrophage (4) most delayed (5) chronic and persistent (6) common with helminths and fungal
Induration
Associated with Tuberculin hypersensitivity, it is soft tissue on skin that is raised and red
Tuberculin skin test
A purified protein derivative from mycobacterium TB injected subcutaneously (induration will form in 48 hrs f person is positive)
