Questions and Answers
What primarily causes the death of CD4+ T cells during HIV replication?
Which of the following infections is most commonly associated with AIDS?
What is a defining characteristic for the diagnosis of AIDS?
Which pathogen is typically isolated in AIDS patients experiencing diarrhea and weight loss?
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Which neurological complications in AIDS can be attributed directly to HIV infection?
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What is the CD4+ T cell count threshold that indicates the progression to AIDS?
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Which condition is associated with severe wasting and diarrhea in AIDS patients?
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Which type of hypersensitivity reaction is impaired in AIDS patients?
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Which malignancy is notably common in individuals with AIDS?
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How do opportunistic infections contribute to morbidity in AIDS?
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Study Notes
Characteristics of Adaptive Immunity
- Adaptive immunity has four key immunologic attributes: antigenic specificity, diversity, immunologic memory, and self/non-self recognition.
Antigenic Specificity
- Vaccination illustrates antigenic specificity as it provides acquired immunity specific to pathogens, such as poliomyelitis virus, without cross-protection against unrelated viruses like influenza.
- Annual influenza vaccinations must target the specific strains due to antigenic variation.
Diversity
- The immune system can generate immense diversity in antigen-recognition molecules (B- and T-cell receptors), enabling recognition of billions of unique epitopes from foreign antigens.
Immunologic Memory
- After exposure to a specific antigen, the immune system retains a memory, leading to a more robust response upon subsequent encounters with the same antigen.
Self/Non-Self Recognition
- The immune system distinguishes self from non-self, responding only to foreign molecules. Misrecognition can lead to autoimmune diseases, some of which may be severe or fatal.
Transplantation Immunology
- Successful transplantation of solid tissues requires immunological compatibility between donor and recipient to minimize rejection.
- Immunosuppressive drugs can facilitate transplant acceptance but may increase infection risk and other health issues.
Types of Transplants
- Autografts: Tissue transplants from the patient to themselves.
- Isografts: Tissue transplants between genetically identical individuals (e.g., identical twins).
- Homografts (Allografts): Transplants between genetically non-identical individuals of the same species.
- Xenografts: Tissue transplants between different species (e.g., pig to human).
Transplant Rejection
- Rejection of homografts/allografts occurs due to antibody-mediated and delayed cellular immune response.
- Types of rejection:
- Hyperacute: Sudden, due to preformed antibodies against the donor's antigens, occurring during surgery.
- Acute: Typically occurs within weeks; can happen later if immunosuppressive therapy fails.
- Chronic: Develops slowly over months or years; involves both antibody- and cell-mediated responses.
Common Immunosuppressive Therapies
- Cyclosporine inhibits IL-2 production, affecting T-cell responses.
- Cyclophosphamide inhibits lymphocyte proliferation.
- Antibodies targeting T-cell antigens reduce T-cell numbers.
Disadvantages of Immunosuppressive Therapy
- Increased risk of infections.
- Side effects like nephrotoxicity from certain drugs (e.g., cyclosporine).
- Heightened cancer risk associated with immunosuppression.
Blood Transfusion Compatibility
- Blood transfusions depend on the compatibility of donor and recipient's RBC blood group antigens.
- Major blood group antigens include ABO system and Rh factor, with potential complications from minor blood group antigens.
ABO Blood Group System
- Four blood groups: A, B, AB, and O based on the presence of A and B oligosaccharides.
- Each group has corresponding natural antibodies; Group AB lacks natural antibodies against A/B antigens.
Severe Combined Immunodeficiency (SCID)
- Results from defects in lymphoid development affecting T/B cells, leading to severe immune dysfunction.
- Thymic aplasia is common, with very low circulating lymphocytes and diminished responsiveness to mitogens.
- High susceptibility to recurrent infections, often fatal in early childhood.
DiGeorge Syndrome (Congenital Thymic Aplasia)
- Characterized by absence of the thymus, resulting from a defect in embryonic development linked to chromosome 22 deletions.
- Innovative treatments using genetically modified lymphoid cells show promise in addressing this severe condition.
Secondary Immunodeficiency
- Nutritional deficiencies can compromise immunity by reducing cell-mediated immune function and CD4+ T helper cells.
- CD4+ T-cell destruction occurs in HIV infections, leading to a decrease in immune regulation.
AIDS Characteristics
- Opportunistic infections often seen, such as Pneumocystis carinii pneumonia and mycobacterial infections (e.g., tuberculosis).
- Neurological complications can arise from direct HIV effects or opportunistic pathogens.
Diagnosis of AIDS
- Confirmation of HIV-1 infection through antibody testing.
- CD4+ T cell counts below 200 cells/mm³ indicate severe immunosuppression.
- Presence of opportunistic infections and malignancies like Kaposi sarcoma.
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Description
This quiz explores the four main immunologic features of adaptive immunity: antigenic specificity, diversity, immunologic memory, and self/non-self-recognition. Understanding these concepts is crucial for comprehending how vaccinations and acquired immunity work. Test your knowledge on the fundamentals of adaptive immunity.
