Investigators have proposed that a molecule known as a superantigen, either made by HIV or an unrelated agent, may stimulate massive quantities of CD4+ T cells at once, rendering them highly susceptible to HIV infection and subsequent cell death. See also Antigen; CD4 (T4) or CD4+ Cells.

An antigen that activates a large percentage of T-lymphocytes.

a viral or bacterial antigen that triggers an immune response from a large number of immune cells (e.g., T-cells) which express a variety of different major histocompatibility (MHC) molecules.

An antigen that interacts with the T cell receptor in a domain outside of the antigen recognition site. This type of interaction induces the activation of larger numbers of T cells compared to antigens that are presented in the antigen recognition site.

Superantigens (SAgs) are a group of virulent toxins that indiscriminately activate T-cells of the immune system causing system-wide inflammation and other serious, potentially fatal symptoms. They are not quite the same as antigens-- though they almost all have antigenic properties-- but rather receive their name from their powers to stimulate a massive antigen-nonspecific immune response.