Human cellular immune response to Giardia lamblia.

Human peripheral blood mononuclear cells (PBMC) from two individuals experimentally and one naturally infected with Giardia lamblia responded strongly (in an in vitro lymphocyte proliferation assay) to both heterologous and homologous (parasite origin) G. lamblia antigen stimuli. Proliferative responses to specific antigens as determined by T-cell blotting were due to Giardia T-cell epitopes mostly present in antigens lower than Mr 85,000 and 31,000 in isolates PM and GS/M-H7, respectively. Additionally, Il-2 production of PBMC respective to T lymphocyte subsets under antigen stimulation were determined in one selected patient. Proliferative and lymphokine responses could be associated with CD4+ PBMC depleted of CD8+ T cells and not with PBMC depleted of CD4+ T cells. These preliminary results suggest the initiation of larger studies addressing questions of cell-mediated immune response and the role of lymphokines in human giardiasis.