Disorders of the immune response Flashcards
Classification of immunodeficiency states
-Primary (congenital or inherited)
-Secondary (acquired later in life)
4 major categories of immune mechanisms
-Humoral or antibody-mediated immunity (B lymphocytes)
-Cell-mediated immunity (T lymphocytes)
-The complement system
-Phagocytosis (neutrophils and macrophages)
The phagocytic system
composed primarily of polymorphonuclear leukocytes and mononuclear phagocytes
Action of Phagocytic system
-migrate to the site of infection
-aggregate around the affected tissue
-envelope the invading microorganisms
-generate microbicidal substances to kill the ingested pathogens
Dysfunction of the phagocytic system
a defect phagocytic function or a reduction in the number of available cells
-Susceptible to candida species, filamentous fungi, and chronic granulomatous disease (CGD)
Adaptive immunity
-development of response to the antigen
-specific humoral and cellular recognition
-memory cells
hypersensitivity disorders
excessive or inappropriate activation of the immune system
Types of hypersensitivity disorders
-Type I IgE-mediated disorders
-Type II antibdy-mediated disorders
-Type III complement-mediated immune disorders
-Type IV T-cell-mediated disorders
Types of IgE-mediated allergic reactions
Atopic disorders- heredity predisposition and production of a local reaction to IgE antibodies produced in response to common environmental agents (Urticaria (hives), allergic rhinitis (hay fever), atopic dermatitis, food allergies, some forms of asthma
Nonatopic disorders- lack the genetic component and organ specificity of the atopic disorders
Phases of type I hypersensitivity reactions
Primary or initial-phase response (vasodilation, vascular leakage, smooth muscle contraction)
Secondary or late-phase response (more intense infiltration of tissues with eosinophils and other acute and chronic inflammatory cells, tissue destruction in the form of epithelial cell damage)
Type II (Cytotoxic) hypersensitivity reactions
mediated by IgG or IgM antibodies directed against target antigens on the surface of cells or other tissue components
Examples of Type II cytotoxic hypersensitivity reactions
-mismatched blood transfusion reactions
-hemolytic disease of the newborn
-certain drug reactions
Type III immune complex allergic disorders
mediated by the formation of insoluble antigen- antibody complexes that activate the complement pathway
Activation of the complement pathway by the immune complex generates…
chemotactic and vasoactive mediators that cause damage by…
-alterations of blood flow, increased vascular permeability, and destructive action of inflammatory cells
Responsible for the vasculitis seen in certain autoimmune disease
Type III immune complex allergic disorders
Type IV hypersensitivity reactions
Cell-mediated Immune response
Cell-mediated immune response
-the principal mechanism of response to a variety of microorganisms, including intracellular pathogens and extracellular agents
-can lead to cell death and tissue injury in response to chemical antigens or self-antigens
basic types of cell-mediated immune response
-direct cell-mediated cytotoxicity (ex; hepatitis)
-delayed-type hypersensitivity (ex; allergic contract dermatitis, hypersensitivity pneumonitis)
Histocompatibility complex
Set of molecules displayed on cell surfaces
-lymphocyte recognition
-antigen presentation
controls the immune response through recognition of “self” and “nonself”
categories of transplanted tissue
*Allogenic- the donor and recipient are related or unrelated but share similar HLA types
*Syngeneic- the donor and recipient are identical twins
*Autologous- the donor and recipient are the same person
Stem cell transplantation
primary immunodeficiency disorders traced to deficiency in stem cells can be cured with allogenic stem cell tx from an unaffected donor
-SCIDs, wiskott-aldrich syndrome, and chronic granulomatous disease
stem cells
can repopulate the bone marrow and reestablish hematopoiesis
-to be effective the bone marrow cells of the host are destroyed by myeloablative doses of chemotherapy
Basic patterns of transplant rejection
-hyperacute reaction
-acute rejection
-chronic host versus graft rejection
hyperacute rejection
- occurs almost immediately after transplantation
-produced by existing recipient antibodies to graft antigens initiating a type III, Arthus-type hypersensitivity reaction
Acute rejection
-occurs within first few months after transplantation with signs of organ failure; may occur months or years after immunosuppression has been terminated
-T lymphocytes respond to antigens in the graft tissue
Chronic host versus graft rejection
-occurs over a prolonged period
-manifests with dense intimal fibrosis of blood vessels of the transplanted organ
the actual mechanism is unclear but may include release of cytokines that stimulate fibrosis
Requirements for GVHD
-The transplant must have a functional cellular immune component
-The recipient tissue must bear antigens foreign to the donor tissue
the recipient immunity must be compromised to the point that it cannot destroy the transplanted cells
Autoimmune diseases
- Systemic lupus (SLE)
-Autoimmune hemolytic anemia (AIHA)
-Pemphigus vulgaris
-Hashimoto thyroiditis
Mechanisms of autoimmune disease
*Heredity and gender
*Failure of self-tolerance
-disorders in MHC-antigen complex/receptor interactions
-molecular mimicry
-superantigens
Criteria for determining an autoimmune disorder
*evidence of an autoimmune reaction
*determination that the immunologic findings are not secondary to another condition
*the lack of other identified causes for the disorder
Transmission of HIV infection
-sexual contact
-blood to blood contact
-perinatally
*transmission from mother to infant is the most common way that children become infected
Phases of HIV infection
- primary infection phase
- chronic asymptomatic or latency phase
- overt AIDS phase
HIV diagnostic methods
- enzyme immunoassay
- western blot antibody detection tests
HIV treatment
-reverse transcriptase inhibitors
-protease inhibitors
-fusion inhibitors
