The effect of conglutinin on production of reactive oxygen species in bovine granulocytes

Conglutinin is a high molecular-weight lectin originally detected in bovine serum. It belongs to the family of collectins that bind sugar residues in a Ca(2+)-dependent manner and are effector molecules in innate immunity. Conglutinin appears to play an important role in immune defense mechanisms, showing antiviral and antibacterial activities when tested in vivo and in vitro. The present study evaluated the effect of conglutinin on the respiratory bursts in bovine peripheral phagocytes. Using nitroblue tetrazolium and hydrogen peroxide assays, we showed that sugar ligand-bound conglutinin stimulated the production of superoxide and H2O2 in granulocytes whereas the non-sugar-bound form of conglutinin inhibited these processes. These results indicate that both forms of conglutinin are able to interact with surface leukocyte receptors but have opposite effects on phagocytic activity. Our findings suggest that conglutinin bound to sugar residues on microbial surfaces can induce oxygen burst in phagocytes, and thereby mediates the elimination of pathogens and prevents the spread of infection.

Bactericidal activity of human serum against strains of Klebsiella from some pathogenic sources

Ten strains of K. pneumoniae were isolated from 225 cases of urinary tract infections, respiratory tract infections and diarrhea [4.4 percent]. They were tested for sensitivity to pooled normal human serum and viable counts were done at 0, 60, 120, 180 minutes. Normal human serum was obtained by pooling the sera from twenty healthy adults who were not receiving antibiotics. Five strains [50 percent] were sensitive to human serum, three strains [30 percent] were resistant to human serum and two strains [20 percent] showed intermediate sensitivity to human serum. Thus the presence of bactericidal action of normal serum on klebsiella may explain the low incidence [4.4 percent] of Klebsiella isolates from different clinical samples