OTH Chapter 8

hypersensitivity

altered immunologic response to an antigen that results in disease or damage to the host

type 1 hypersensitivity

against environmental antigens

• IgE binds to Fc receptors on surface of mast cells where histamine is released

type 1 hypersensitivity manifestations

• GI allergy

  • vomiting, diarrhea, abdominal pain

• skin

  • hives

• mucosa allergens

  • conjunctivitis, rhinitis, asthma

• lung allergens

  • asthma, bronchospasm, edema, thick secretions

type 2 hypersensitivity

specific cell/tissue is the target of an immune response

• symptoms depend on tissue/organ involved

type 2 hypersensitivity mechanisms that can affect cells

• cell is destroyed by antibodies and complement

• cell destruction through phagocytosis

• tissues damaged by products of neutrophils

• antibody-dependent cell-mediated cytotoxicity

• target cell malfunction

type 3 hypersensitivity

immune-complex mediated

• antigen-antibody complexes are formed in the circulation and are later deposited in vessel walls or extravascular tissues

• not organ specific

type 3 hypersensitivity manifestations

• serum sickness

  • caused by formation of immune complexes in blood and deposition in target tissues

• arthus reaction

  • vasculitis caused by repeated local exposure

type 4 hypersensitivity

cell-mediated which does not involve antibodies

• cytotoxic t lymphocytes or lymphokine-producing TH1 and TH17 cells

  • direct killing of phagocytic cells

examples of type 4 hypersensitivities

• graft rejection

• tb skin test

• allergic rxns from poison ivy or metals

allergy

deleterious effects of hypersensitivity to environmental antigens

autoimmunity

disturbance in the immunologic tolerance of self-antigens

alloimmunity

immune rxn to tissues of another individual

immune deficiency

rxn insufficient to protect the host

allergens

environmental antigens that cause atypical immunologic responses

• pollens, molds, fungi, foods, animals, cigarette smoke, house dust

anaphylaxis

most rapid and severe immediate hypersensitivity rxn

• systemic or cutaneous

desensitization

may reduce the severity of the allergic rxn but could also cause anaphylaxis

autoimmunity

genetic, environmental, and random factors

systemic lupus erythematosus

chronic multisystem inflammatory disease

• autoantibodies against

  • nucleic acids

  • histones

  • ribonucleoproteins

  • other nuclear materials

what are the symptoms of systemic lupus erythematosus the result of

type 2 or 3 hypersensitivity rxns

systemic lupus erythematosus clinical manifestations

• vasculitis and rash

• arthralgias/arthritis

• renal disease

• hematologic changes

• cardiovascular disease

transfusion rxns

occurs when person with one blood type receives another

Type O

universal donor

type AB

universal recipient

transplant rejection

MHCs are major target

• classified according to time

  • hyperacute

    • immediate and rare

    • preexisting antibody to the antigens of the graft

  • acute

    • days to months

    • cell-mediated immune response

  • chronic

    • months or years

    • weak cell-mediated rxn against minor HLA antigens

primary immune deficiencies

• usually from a single gene defect

• not inherited

severe combined immunodeficiency

• few detectable lymphocytes

• underdeveloped thymus

• absent or reduced IgM and IgA levels

bare lymphocyte deficiency

adequate b and t-cells but they don’t work

• inability to produce MHC class 1 and 2

wiskott-aldrich syndrome

depressed IgM production w/ bleeding

digeorge syndrome

lack of thymus and parathyroid gland

• Ca2+ deficiency

predominantly antibody deficiencies

defective b-cell development

complement deficiencies

• C3 deficiency

  • most severe due to central role in complement cascade

  • results in recurrent life-threatening infections

• mannose-binding lectin deficiency

  • defect of lectin pathway

  • results in risk of infection

treatment for primary immune deficiencies

• iv immune globulin

• stem cell transplantation

• transfusion of erythrocytes

• bone marrow transplants

• mesenchymal stem cell injection

most people with malignancies will die from the infection or the tumor

the infection due to deficiency of immune response

immunosuppressive treatments

• corticosteroids

• chemotherapeutic agents

• irradiation

• antirejection drugs

acquired immunodeficiency syndrome (AIDS)

most advanced stage of infection of infection by HIV

• depleted body’s TH cells

• creates generalized immune deficiency

HIV epidemiology

• blood-borne pathogen

• most common in heterosexual activity and women

HIV structure

• retrovirus

• genetic info is RNA (reverse transcriptase)

HIV life cycle

• attachment to target cell

• viral capsid released into target cell cytoplasm

• viral rna inserted into target cell’s genetic material

• formation/release of new virions

HIV clinical manifestations

• serologically negative → no detectable antibody

• serologically positive but asymptomatic → positive for antibody against HIV proteins

• early stages

  • resembles the flu

  • disappears after 1-6 weeks

• AIDS

  • atypical or opportunistic infections and cancers

  • debilitating chronic disease

diagnosis and treatment of AIDS/HIV

• decreased CD4+ t cell numbers

• antiretroviral therapy

pediatric AIDS

transmitted during pregnancy, at delivery, breast-feeding

• treatment must begin at time of diagnosis