In vivo response of mast cells to lepromatous serum.

: Adult healthly mice of pure line Institute strain were given, into the foot pad, an intradermal injection of normal human serum in group A and lepromatous serum in group B. In both groups, the animals were killed at varying time intervals. Serial paraffin sections of the foot pad skin 5--7 mu thick, were cut and stained with haematoxylin and eosin, toludine blue, acridine orange and para-bromaniline. On comparing the two groups, in group B the response of mast cells was more prompt, pronounced and persistant. The increase in the number of cells was accompanied by explosive degranulation around nerves, blood vessels and muscles. This response became less by 15 days but did not disappear completely. There were still few intact cells in the dermis. Histamine, heparin and 5-Ht showed a corresponding rise. The importance of the findings is discussed.