Alloimmune mice (mice that have been exposed to cells from another murine strain) were shown to make antibodies against gp120 and p24 of human immunodeficiency virus (HIV), and mice of the autoimmune strains MRL-lpr/lpr and MRL-(+)/+ made antibodies against gp120. This is surprising because the mice were not exposed to HIV. Furthermore, anti-anti-MHC antibodies (molecules that have shapes similar to those of major histocompatibility complex molecules) were detected in both alloimmune sera and MRL mice. These results are discussed in the context of a possible role for allogeneic stimuli in the pathogenesis of acquired immunodeficiency syndrome, as suggested by an idiotypic network model.

Considerations from a network theory of the immune system suggest that human immunodeficiency virus and allogeneic stimuli may act synergistically to cause AIDS. The immune responses to these stimuli include two components that are directed against each other. In some AIDS risk groups other antigens that mimic major histocompatibility complex antigens may substitute for allogeneic stimuli. Implications for the prevention of AIDS are discussed.The idea that human immunodeficiency virus (HIV) is the sole cause of AIDS (without any cofactors) and is directly responsible for the depletion of CD4-bearing T cells is currently being questioned by many researchers for several reasons. A surprisingly low number of T cells are infected with HIV in AIDS (1), and immunosuppression occurs prior to depletion of CD4 cells (2). Furthermore, immunity against HIV does not protect against AIDS; AIDS patients have high quantities of anti-HIV antibodies in their sera (3) and generate a strong anti-HIV cytotoxic T-cell response (4) but are not protected. In fact, people tend to become seriously ill only after they make anti-HIV antibodies. In spite of intensive research, a detailed mechanism explaining T-cell depletion in vivo, only on the basis of HIV infection, has not been characterized.An alternative possibility being considered by several groups of researchers is that HIV induces a deleterious immune response that attacks the immune system itself (5-15). In this paper, we describe an immunological process that could lead to AIDS. Network RegulationThe recognition of variable (V) regions by lymphocytes and vice versa is widely believed to be a central aspect of the specific regulation of the immune system (16). The relative levels ofpopulations oflymphocytes and the topology oftheir interactions are then key aspects of a description of the system. Some lymphocyte populations recognize an invading antigen, and some have V regions that functionally resemble the antigen in that they have complementarity to the V regions of antigen-specific clones. Specific interactions between these populations are believed to regulate the immune response. An explicit network model accounts for a considerable range of phenomena, including memory, separate roles for IgM and IgG, helper T cells, suppressor T cells, and specific T-cell factors (10,11,(17)(18)(19)(20)(21).The theory we describe here emerges from that model. An important component of the theory is the concept of network focusing, which refers to the ability of the network to select clones that are images of particular antigens, including self antigens. A second component is the idea that there is a major axis of specificities in the immune system, bounded by self class I and class II major histocompatibility complex (MHC) antigens. We suggest AIDS is a consequence of a destabilization of the system after excessive stimulation along its major axis.T (Fig. 1). Each suppressor T cell is idiotypically connected to a large number of helper T cells and the suppressor T cells are said ...

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