Asteroid body in sporotrichosis. Yeast viability and biological significance within the host immune response.

The asteroid body in Sporotrichosis (AB) is a characteristic structure that allows diagnosis in lymphangitic presentations and whose generation and composition is not fully understood. Our study focused on the biological relationship between the yeast and host elements present in the AB. Indirect immunofluorescence showed that on ABs obtained from naturally infected individuals there were antigenically related IgG and IgM molecules in the spikes of the radiated crowns. However, there were differences in the pattern of distribution for each immunoglobulin isotypes. The yeast cells located at the center of the ABs were viable, as shown by the generation of germ tubes and conidial formation after 36-48 hours of incubation at 22 degrees C. The central yeast could divide and proliferate even in the ABs that had been pre-treated with specific anti-Sporothrix schenckii serum and fresh complement. The data suggests that AB in sporotrichosis might be a resistance structure which uses the host immune molecules to the advantage of the yeast.