In vitro interactions between macrophages and aluminum-containing adjuvants

Intramuscular administration of aluminum-adjuvanted vaccines induces an infiltration of aluminum-containing macrophages between muscle fibers. In vitro stimulation of human monocyte-derived macrophages with aluminum hydroxide (AlOOH) induces similar intracellular crystalline inclusions as well as phenotypical and functional modifications. We compared in this study the ability of other adjuvants to exert similar changes in macrophages in vitro. All mineral salts, i.e. aluminic (AlOOH, AlPO4) and non-aluminic mineral adjuvants (CaPO4, FePO4) but not emulsion were able to increase macrophages capacity to potentiate autologous memory T lymphocyte proliferation, while only aluminic adjuvants induced CD83 expression and increased CD86 on macrophages. All together, this suggests that aluminic and non-aluminic adjuvants exerted their immunoactivities by distinct mechanisms on macrophages.