medical summaries

EPSTEIN-BARR VIRUS (EBV) SEROLOGY   A. Description.EBV is the causative agent of Burkitt’s lymphoma, nasopharyngeal carcinoma, and most commonly, infectious mononucleosis (IM). The virus is ubiquitous; 80% to 90% of healthy adults have EBV antibodies. EBV infects B lymphocytes. B. Infectious mononucleosis (IM) is an acute, self-limiting disease typically seen in young adults. The disease is characterized by fever, sore throat, cervical lymphadenopathy, splenomegaly, and mild hepatitis. TheWBCcount is elevated, and reactive lymphocytes are seen in the peripheral blood. There is a relative and absolute lymphocytosis. The average incubation period is approximately 2 to 8 weeks (see Web Case Study 5–2). C. Antigens and antibodies 1. Viral capsid antigen (VCA) is found in the cytoplasm of EBV-infected lymphocytes. IgM antibodies against VCA are detectable early in the infections, but disappear within 2 to 4 months. IgG antibodies against VCA de...

HEPATITIS     is an inflammation of the liver and usually refers to the diseases caused by a group of viruses identified as hepatitis A, B, C, D, and E. A. Hepatitis A (infectious hepatitis) is caused by the hepatitis A virus (HAV). 1. Transmission. HAV is transmitted most commonly through the fecal-oral route and is frequently seen in epidemics in areas with poor sanitation. Raw shellfish from contaminated water can also transmit the disease. 2. Disease course. HAV infections are almost always acute and self-limiting. There is no carrier state. Symptoms, if present, are vague and relatively nonspecific; patients may complain of fatigue, malaise, and anorexia. Jaundice may be present, although most patients are anicteric. Many cases are subclinical, especially those in children. 3. Laboratory diagnosis. Liver function test results, especially alanine aminotransferase (ALT), are elevated. Total bilirubin levels may be elevated. Antibod...

SYPHILIS SEROLOGY   A. Human syphilis is caused by the spirochete Treponema pallidum . Antibodies against treponemal antigens and nontreponemal cardiolipin antigens (Wasser-mann antigens) develop and elicit a cell-mediated and humoral Ir, which results in the formation of immune complexes. B. Disease. Sexual contact with infected persons is the most common form of transmission of human syphilis. Transmission through blood or blood-product transfusion can occur but is rare now because of effective pretransfusion testing. In addition, syphilis can be passed from an infected pregnant woman to her fetus. There are four clinical stages of disease. 1. Primary (early) syphilis. Inflammatory lesions (chancres) appear 2 to 8 weeks after infection and last for 1 to 5 weeks. Serum tests for syphilis are positive in 90% of patients after 3 weeks. The antibodies that develop are predominantly IgM. 2. Secondary syphilis usually occurs 6 to 8 weeks af...

AUTOIMMUNITY     is an expression of the Ir that occurs when the body’s selftolerance system fails. The body’s immune cells are no longer able to recognize “self” and thus mount an Ir against its own antigens. This can result in a variety of apparently unrelated diseases known as autoimmune diseases. However, all autoimmune diseases involve immune complexes. The autoimmune response is strongly influenced by MHC antigens and can involve either Class I or Class IIMHCproteins.Many autoimmune diseases are associated with specific Class II human leukocyte antigens (HLA), and determining an individual’s HLA type can help predict the risk of certain diseases .

MAJOR HISTOCOMPATIBILITY COMPLEX A. In transplantation studies, MHC gene products were identified as responsible for graft rejection. Likewise, studies on responses to antigens, demonstrated thatMHCgene products were found to control immune responses. It was determined that antigen-specific T cells recognize portions of protein antigens that are bound noncovalently to MHC gene products. B. The Major histocompatibility complex is found on human chromosome 6. 1. Have a role in intercellular recognition and discrimination of self/nonself. 2. Have a role in development of humoral and cell-mediated immune responses. 3. One’s set of MHC genes influences the repertoire of antigens to which that person’s T H and T C cells can respond, therefore, one’s MHC plays a role in susceptibility to disease and autoimmunity. C. Organization of MHC is summarized in Table 5–4. 1. Class I MHC are glycoproteins found on most nucleated ...

  may be natural acquired or IMMUNITY   A. Natural immunity is present at birth and provides protection against disease and aids in recovery from disease. However, it also provides the basis for organ rejection after transplantation. Factors involved in natural immunity include : 1- Physical barriers such as skin and mucous membranes . Genetically controlled 2-susceptibility and nonsusceptibility to certain diseases . , 3. Inflammation which involves a vascular response and a cellular response by phagocytic cells . Acute-phase plasma protein such as C-reactive protein, haptoglobin, and fibrinogen which are produced in response to injury and aid in wound healing   B. Acquired or specific immunity results when immunologic memory and antibody specific to a foreign antigen develop in response to the antigen. Acquired immunity may be active ( through immunization or disease) or passiv...