The pathogenesis of HIV has been evaluated by many investigators, yet the precise reasons for certain patients developing lethal infection while others appear to live for long periods tolerating the HIV virus remain to be determined. The immune response to HIV may be critical in the development of the fatal infected stated, while tolerance of the HIV virus may allow longer-term survival despite infection. The mechanisms for failure of immune protection from HIV and the subsequent development of immunodeficiency are likely related to the very nature of the immune response to the initial HIV infection.