The Journal of Medical Microbiology, Vol 46, Issue 3 251-255, Copyright © 1997 by Society for General Microbiology
Pre-treatment with Concanavalin-A increases resistance of mice to peritoneal infection by Serratia marcescens
S. M. Arraes, L. C. Gaziri, M. C. Vidotto, H. O. Saridakis and I. Felipe
Laboratory of Clinical Immunology, Universidade Estadual de Maringa, Brazil.
Mice pre-treated with Concanavalin-A largely survived an intra-peritoneal
inoculum of 2 x 10(7) Serratia marcescens, whereas all control mice died
within 15 h of inoculation. A subpopulation of peritoneal macrophages from
Con-A pre-treated mice was able to phagocytose the bacteria in vitro (6.7
SEM 1.2% phagocytosing cells) and in vivo (16.9 SEM 2.1%), whereas control
phagocytes did not phagocytose S. marcescens. The survival of Con-A
pre-treated mice allowed their immunisation with living bacteria, and the
antiserum thus produced increased the phagocytosis of S. marcescens in
vitro. Control mice largely survived an inoculum of S. marcescens suspended
in 50% immune serum, although the bacteria were resistant to the
bactericidal activity of that serum. These results suggest that, in
contrast to the delayed humoral protection afforded by immunisation,
phagocytosis by phagocytes activated by Con-A conferred early protection to
mice against experimental infection by S. marcescens.
