[Seeking a causative agent of sarcoidosis].

Bacterial components (MDP and IT27 antigen), demonstrated in sarcoid granulomas, strongly suggest the causative agent of sarcoidosis to be derived from some bacteria but many kinds of bacteria are known to have these bacterial components. Our PCR detection of mycobacterial DNA could not demonstrate a significant contribution of M. tuberculosis to the pathogenesis. We then developed a monoclonal antibody to the causative agent by immunizing mice with a crude homogenate of the affected lymph nodes. Hybridized spleen cells were checked with ELISA and all the Ig-producing cell colonies were examined by immunostaining on paraffin sections of lymph nodes with sarcoidosis or tuberculosis. The established antibody (SG5) recognized some extrinsic antigens sequestrated in sarcoid granulomas, in a similar pattern of distribution to those of the bacterial component of MDP and the bacterial product of IT-27. Moreover, ELISA analysis of the SG5 antibody revealed a specific reactivity to culture supernatant of P. acnes. By the immunization of mice with a crude bacterial extract of P. acnes, we recovered one clone of hybridoma named PAB antibody, that possessed an identical reactivity to that of SG5 antibody, as far as examined by ELISA and immunohistochemistry. Furthermore, PCR detection of P. acnes DNA resulted in 92% (36/39) positive in the lymph nodes with sarcoidosis and 41% (12/29) in the control lymph nodes, with a significant difference (p < 0.001, by Fisher's Probability Test) between these two groups.(ABSTRACT TRUNCATED AT 250 WORDS)