Opsonic effect of jacalin and human immunoglobulin A on type II group B streptococci.
This study examined the effect of immunoglobulin A (IgA) and the IgA-binding lectin jacalin on the phagocytosis of type II group B streptococci (GBS). Strains possessing the trypsin-sensitive and trypsin-resistant components of the c protein (II/c) and type II GBS lacking the c protein (II) were examined by radiolabeled bacterial uptake, bactericidal assays, and electron microscopy. Type II/c GBS resisted phagocytosis by monocytes (4.9% +/- 0.8% uptake, mean +/- SE, n = 25) compared with type II GBS (8.5% +/- 1.4% uptake, n = 14, P = 0.03). Phagocytic killing by polymorphonuclear leukocytes was also less for the type II/c strain 78-471 than for the type II strain 79-176 (68% +/- 5% versus 86% +/- 4% reduction in CFU at 45 min, P = 0.03). IgA binding did not explain the resistance of type II/c GBS to phagocytosis. The uptake of type II/c GBS was not significantly different after opsonization in cord sera lacking endogenous IgA (5.93% +/- 1.4%) than in the same cord sera after addition of exogenous IgA (5.48% +/- 1.4%, P = 0.69, n = 9). Attempts to remove serum IgA with the IgA-binding lectin jacalin resulted in the binding of IgA-jacalin complexes to II/c GBS. This combination of nonspecific IgA and jacalin increased uptake of II/c GBS from 4.9% +/- 0.8% to 11.8% +/- 1.9% (P = 0.002). Jacalin also combined with specific, immune, monoclonal IgA bound to the surface of Haemophilus influenzae and promoted the uptake of these bacteria. Jacalin and IgA mediated phagocytosis of II/c GBS via receptors that were not dependent on divalent cations and that were not modulated by plating monocytes on antigen-antibody complexes.
Payne
N R
NR
Department of Pediatrics, University of California-Los Angeles School of Medicine, Harbor-UCLA Medical Center, Torrance 90502.
Concepcion
N F
NF
Anthony
B F
BF
D000936:Antigen-Antibody Complex; D001770:Blood Bactericidal Activity; D002478:Cells, Cultured; D006193:Haemophilus influenzae / Q000276:immunology; D006801:Humans; D007070:Immunoglobulin A / Q000276:immunology*; D037102:Lectins / Q000276:immunology*; D009000:Monocytes / Q000382:microbiology*; D009504:Neutrophils / Q000276:immunology / Q000648:ultrastructure; D009895:Opsonin Proteins; D010587:Phagocytosis; D037121:Plant Lectins; D013292:Streptococcus agalactiae / Q000276:immunology* / Q000648:ultrastructure
D000936:Antigen-Antibody Complex; D007070:Immunoglobulin A; D037102:Lectins; D009895:Opsonin Proteins; D037121:Plant Lectins; C043696:jacalin