Human Anatomy & Physiology (9th Edition)

Published by Pearson
ISBN 10: 0321743261
ISBN 13: 978-0-32174-326-8

Chapter 21 - The Immune System: Innate and Adaptive Body Defenses - Review Questions - Critical Thinking and Clinical Application Questions - Page 799: 1e

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# similarities : i- both SCIKD and AIDS cause severe immunodeficiency leaving the body subjected to infection with Opportunistic organisms ( viral, bacterial, fungal. and protozoal ). ii- development of cancer due to concomitant EBV infection in both cases. # Dissimilarities : A- SCID : - primary immunodeficiency. - congenital defects in the development of the cells of the immune system. - failure of differentiation of stem cells into T and B cells. - treated by bone marrow grafting. B- AIDS : - secondary immunodeficiency. - viral infection ( acquired ) by Human Immunodeficiency Virus ( HIV ). - HIV attacks CD4 helper T cells leading to their depletion. - controlled by Antiviral drugs e.g Azidothymidine ( AZT ), dideoxyinosine ( ddI ), deoxythiacytidine ( 3 TC ) and stavudine ( d4T ). Severe Combined Immunodeficiency ( SCID ) - this may be due to failure of differentiation of stem cells into T and B cells however the explanation of this failure is not known. - both humoral and cell mediated immunity are deficient. - these infants suffer from all kinds of opportunistic infections : viral, bacterial, fungal and protozoal. - death occurs early in childhood ( before 1 year ). - the disease may be inherited in an X-linked recessive or autosomal recessive manner, however sporadic forms occur. # Immunologic Findings : 1- Hypoplasia of the Thymus as shown by chest X-ray. 2- Lymphopenia and decreased T cell number and functions: - impaired response to Phytohemagglutinin ( PHA ). - Impaired Delayed Hypersensitivity reactions. 3- Decreased B cell number and function : - Serum Immunogloulins are absent or decreased - No response to antigenic stimuli. # Treatment : patients may be made completely normal by grafting with histocompatible bone marrow from a sibling. incompatible grafts will lead to a fatal " graft versus host " ( GVH ) reactions. - Gammaglobulins may be administered. - Antibiotics are used for treatment of infections. Epstein-barr virus ( EBV ) - EBV is the causative agent of infectious mononucleosis - it is one of the tumor viruses.( causal relation between EBV and human cancer ). - it is associated with Burkitt s Lymphoma, Nasopharyngeal Carcinoma ( NPC ) and lymphoproliferative disorders in immunodeficient individuals. Infectious Mononucleosis - EBV is transmitted by infected saliva. - infection starts in the oropharynx, then the virus infects B lymphocytes which are tramsformed and proliiferate. - EBV remains latent in lymphocytes but viral antigens are expressed e.g. nuclear antigen ( EBNA ). these cells are rejected by activated T Lymphocytes. this leads to appearance of atypical T Lymphocytes in the peripheral blood. - the disease manifests by fever, sore throat, enlarged lymph nodes and spleen, rash may appear. - it is a self limited disease.
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