Cholera toxin and Escherichia coli heat-labile enterotoxin, but not their nontoxic counterparts, improve the antigen-presenting cell function of human B lymphocytes.
B lymphocytes play an important role in the immune response induced by mucosal adjuvants. In this study we investigated the in vitro antigen-presenting cell (APC) properties of human B cells upon treatment with cholera toxin (CT) and Escherichia coli heat-labile enterotoxin (LT) and nontoxic counterparts of these toxins, such as the B subunit of CT (CT-B) and the mutant of LT lacking ADP ribosyltransferase activity (LTK63). Furthermore, forskolin (FSK), a direct activator of adenylate cyclase, and cyclic AMP (cAMP) analogues were used to investigate the role of the increase in intracellular cAMP caused by the A subunit of CT and LT. B lymphocytes were cultured with adjuvants and polyclonal stimuli necessary for activation of B cells in the absence of CD4 T cells. Data indicated that treatment with CT, LT, FSK, or cAMP analogues, but not treatment with CT-B or LTK63, upregulated surface activation markers on B cells, such as CD86 and HLA-DR, and induced inhibition of the proliferation of B cells at early time points, while it increased cell death in long-term cultures. Importantly, B cells treated with CT, LT, or FSK were able to induce pronounced proliferation of both CD4(+) and CD8(+) allogeneic T cells compared with untreated B cells and B cells treated with CT-B and LTK63. Finally, only treatment with toxins or FSK induced antigen-specific T-cell proliferation in Mycobacterium tuberculosis purified protein derivative or tetanus toxoid responder donors. Taken together, these results indicated that the in vitro effects of CT and LT on human B cells are mediated by cAMP.
Negri
Donatella R M
DR
Department of Infectious, Parasitic and Immune-Mediated Diseases, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy. donatella.negri@iss.it
Pinto
Dora
D
Vendetti
Silvia
S
Patrizio
Mario
M
Sanchez
Massimo
M
Riccomi
Antonella
A
Ruggiero
Paolo
P
Del Giudice
Giuseppe
G
De Magistris
Maria Teresa
MT
D000938:Antigen-Presenting Cells / Q000276:immunology*; D001402:B-Lymphocytes / Q000737:chemistry / Q000276:immunology*; D051940:B7-2 Antigen / Q000032:analysis; D001427:Bacterial Toxins / Q000276:immunology* / Q000633:toxicity; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D049109:Cell Proliferation; D002478:Cells, Cultured; D002772:Cholera Toxin / Q000276:immunology* / Q000633:toxicity; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000494:pharmacology; D004768:Enterotoxins / Q000276:immunology* / Q000633:toxicity; D020536:Enzyme Activators / Q000494:pharmacology; D029968:Escherichia coli Proteins / Q000276:immunology* / Q000633:toxicity; D006684:HLA-DR Antigens / Q000032:analysis; D006801:Humans; D007155:Immunologic Factors / Q000494:pharmacology; D008213:Lymphocyte Activation
D051940:B7-2 Antigen; D001427:Bacterial Toxins; D004768:Enterotoxins; D020536:Enzyme Activators; D029968:Escherichia coli Proteins; D006684:HLA-DR Antigens; D007155:Immunologic Factors; D005576:Colforsin; D002772:Cholera Toxin; C027538:heat-labile enterotoxin, E coli; D000242:Cyclic AMP