Granuloma formation induced in mice by chemically defined mycobacterial fractions

Amounts of trehalose-6,6-dimycolate as small as 1 to 5 mug can, after intravenous injection, induce in the lungs of mice formation of tubercles in which the cellular composition is indistinguishable from that in tubercles formed after an infection with living BCG bacilli. The strongest cellular response in mice was induced by cord factor from Mycobacterium kansasii; the weakest was induced by cord factor from the BCG strain of M. bovis. It was found that three intravenous injections of cord factor induced a more extensive cellular response than did one injection of the same total amount of cord factor. Mice treated intravenously with cord factor were protected against an intravenous challenge with the virulent H37Rv strain of M. tuberculosis. The cellular response in the lungs of mice to intraperitoneal injections of living BCG and cord factor was very weak compared with that after intravenous injections. Intraperitoneal vaccination of mice with cord factor did not protect the mice against a challenge with virulent tubercle bacilli. Mice vaccinated intraperitoneally with BCG were immunized although no granulomas, or very few, were present in the lungs at the time of the challenge. The significance of the cellular response induced by cord factor is discussed.

"Residual bodies" in sarcoid and sarcoid-like granulomas

A MORPHOLOGICAL AND HISTOCHEMICAL STUDY WAS MADE OF EPITHELIOID CELL GRANULOMAS: (a) classical sarcoid type, namely, sarcoidosis, Kveim tests, tuberculosis, farmer's lung, and Crohn's syndrome; (b) sarcoid-like granulomas, often distinguishable from (a) by the presence of extracellular mucin or bile, namely, ulcerative colitis, diverticulitis, cholecystitis, cholangitis, carcinoma of the rectum and lymph nodes, draining tumours. All these granulomas showed similar, numerous cytoplasmic granules in epithelioid and giant cells with the properties of residual bodies, i.e., end products of activated lysosomes. The presence of residual bodies demonstrates the following features the morphological similarity of the granulomas studied, and the phagocytic nature of the affected cells. It suggests a common mechanism of granuloma formation but does not identify any particular exogenous cause. The findings suggest that Boeck's sarcoidosis may be caused by unidentified exogenous agents.