Enhancing effect of murine polymorphonuclear neutrophils (PMN) on the multiplication of Blastomyces dermatitidis in vitro and in vivo.

The purpose of this study was to determine the effect of murine polymorphonuclear neutrophils (PMN) on the multiplication of the fungal pathogen Blastomyces dermatitidis in vitro and in vivo. With a newly devised method, PMN were obtained in adequate numbers (7 X 10(6) per mouse) and purity (92%) for these studies. In 24 h co-cultures PMN, but not lymph node cells (LNC), enhanced the replication of virulent (V) and avirulent (AV) strains of B. dermatitidis 61% and 34%, respectively. In 72 h co-cultures, multiplication was enhanced even more (V, 180%; AV, 140%), when compared to cultures of B. dermatitidis in medium alone. Viability of PMN was not required, because PMN lysates, but not LNC lysates, were effective in enhancing multiplication. Subcutaneous injection of B. dermatitidis mixed with PMN enhanced multiplication by 90% compared to V alone in a subcutaneous abscess model, whereas mixing with LNC did not enhance multiplication. When AV, a strain which does not by itself replicate in vivo, was injected in vivo with PMN it increased 2.75-fold over 4 days. These findings document the in vivo significance of in vitro enhancement of B. dermatitidis replication by PMN, and support the contention that accumulation and death of PMN in B. dermatitidis lesions may exacerbate this infection in its early stages.