1.INTRODUCTION In June 1981, the centers for The Disease Control of the United States reported that five young homosexual men in the Los Angels area had contracted Pneumocystis Carinii pneumonia( a kind of pneumonia that is particularly found in AIDS patient). 2 of the patients had died. This report signalled the begninning of an epidemic of a viral disease characterized by immunosuppression associated with opportunistic infection( an infection caused by a microrganism that does not normally produce disease in human; it occurs in persons with ....