Selective inhibition of the in vitro murine B lymphocyte response by pentamidine

A study was undertaken on the immunomodulating properties of pentamidine, a diamidine used in the treatment of African trypanosomiasis, pneumocystosis and leishmaniasis. Pentamidine inhibited the ability of mouse splenic lymphocytes to respond to mitogens. In particular inhibition of the B lymphocyte response was observed. At concentrations of 1 microgram/ml (1.7 x 10(-6) M), pentamidine markedly inhibited the response to the B cell mitogen, lipopolysaccharide (LPS), while concentrations of 10 micrograms/ml had to be attained to produce a similar effect on the response to the T cell mitogens phytohaemagglutinin (PHA) and concanavalin A (ConA). Further studies showed that pentamidine was not toxic to either resting or proliferating cells and probably acts by interacting directly with B cells rather than modifying the regulatory cell populations.