Th1-Th2 cytokine kinetics in the bronchoalveolar lavage fluid of mice infected with Cryptococcus neoformans of different virulences

Th1 immune response plays an important role in protection against infection with Cryptococcus neoformans in mice. We investigated the effect of virule nce of C, neoformans on cytokine production in the lung of a mouse model of pulmonary cryptococcosis, BALB/c mice were inoculated intratracheally with a high or low virulence strain of C, neoformans, followed by serial measur ements of Th1 and Th2 cytokine concentrations in the bronchoalveolar lavage (BAL) fluid using appropriate enzyme-linked immunosorbent assay kits. The number of colony-forming units (CFU) increased with time, and all mice infe cted with the highly virulent strain were dead at 28 days after inoculation , In contrast, the number of microorganisms diminished with time in the mic e infected with the low virulence strain during the 4-week study. The numbe rs of neutrophils and lymphocytes in the BAL fluid paralleled those of CFU, High neutrophil counts were observed in the BAL fluid of mice infected wit h the highly virulent strain, while lymphocyte counts were increased only i n the later part of the study in mice infected with the high and low virule nce strains. The concentrations of Th2 cytokine, interleukin (IL)-4 were si gnificantly higher in mice infected with the highly virulent strain at days 14 and 21 of infection, whereas the level of Th1 cytokine, interferon-gamm a, was significantly higher in the latter strain at days 7 and 14, Our resu lts suggest that strain-specific difference in the organism's ability to in duce (or evade) the host immune system contributes to the outcome of infect ion.