Lysozyme and angiotensin converting enzyme levels in experimental mycobacterial granulomas

A study has been made on mycobacterial-induced granulomas in guinea-pig lymph nodes. Lysozyme and angiotensin-converting enzyme (ACE) were measured in the auricular lymph nodes and serum of guinea-pigs which had received live BCG (Pasteur) or Cobalt (Co)-irradiated armadillo-derived Mycobacterium leprae intradermally into the ear or dinitrofluorobenzene (DNFB) painted epicutaneously upon the ears. In the lymph nodes with granulomas induced by either live BCG or killed M. leprae, the mean concentrations of lysozyme and ACE varied directly with the mean weight of the lymph nodes but the temporal pattern of weight change differed with the two agents. In M. leprae recipients at the time of peak lymph node weight, serum lysozyme and ACE values were significantly greater than those observed in controls; in animals receiving live BCG (Pasteur), serum lysozyme but not ACE values were elevated significantly at the time of peak lymph node weight. Four days following the epicutaneous application of DNFB, where there was no granuloma, there was a similar increase in the concentration of lysozyme and ACE in the lymph nodes. At the same time, there was also significant elevation in the serum lysozyme and ACE concentrations. Thus, in the granulomatous responses, the parallel tissue and serum changes in lysozyme and ACE concentrations were consistent with increased production and secretion of each enzyme by cells of the mononuclear phagocyte series. The increased lysozyme and ACE concentrations found in the lymph nodes of DNFB sensitised animals gives further evidence that such changes are not unique to granulomas. Finally, the intradermal administration of dead M. leprae in guinea pigs also produced increased lysozyme and ACE levels similar to that found in leprosy in man.