Tham khảo tài liệu 'saladin anatomy and physiology the unity of form and function episode 13', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | I Text Saladin Anatomy Physiology The Unity of Form and Function Third Edition 21. The Lymphatic and Immune System The McGraw-Hill Companies 2003 832 Part Four Regulation and Maintenance dothymidine AZT or Retrovir which inhibits reverse transcriptase and prolongs the lives of some HIV-positive individuals. AZT is now recommended for any patient with a CD4 count below 500 cells L but it has undesirable side effects including bone marrow toxicity and anemia. The FDA has approved other drugs including dideoxyinosine ddI and dideoxycytidine ddC for patients who do not respond to AZT but these drugs can also have severe side effects. Another class of drugs protease inhibitors inhibit enzymes proteases that HIV needs in order to replicate. In 1995 a triple cocktail of two reverse transcriptase inhibitors and a protease inhibitor was proving to be highly effective at inhibiting viral replication but by 1997 HIV had evolved a resistance to these drugs and this treatment was failing in more than half of all patients. Alpha interferon has shown some success in inhibiting HIV replication and slowing the progress of Kaposi sarcoma. There remain not only these vexing clinical problems but also a number of unanswered questions about the basic biology of HIV. It remains unknown for example why there are such strikingly different patterns of heterosexual versus homosexual transmission in different countries and why some people succumb so rapidly to infection while others can be HIV-positive for years without developing AIDS. AIDS remains a stubborn problem sure to challenge virologists and epidemiologists for many years to come. We have surveyed the major classes of immune system disorders and a few particularly notorious immune diseases. A few additional lymphatic and immune system disorders are described in table . The effects of aging on the lymphatic and immune systems are described on page 1111. Before You Go On Answer the following questions to test your understanding .
