We examined the functional importance of
immunoglobulin polypeptide fragments generated by
Pseudomonas aeruginosa elastase (Pseudomonas
elastase). The purpose of this study was to determine whether the
elastase produced by Pseudomonas aeruginosa cleaves human
IgG into immune fragments that functionally inhibit opsonophagocytosis. Our results confirm that
IgG isolated from patients with
cystic fibrosis (CF) incubated with purified pseudomonas
elastase results in the generation of two major
polypeptide fragments and that, furthermore, these fragments significantly inhibit bacterial uptake by human neutrophils. After 75 minutes bacterial uptake was six times greater when intact
IgG was used as an
opsonin (uptake 90.2% +/- 18.6% SEM) compared with a
IgG was used as an
opsonin (uptake 90.2% +/- 18.6% SEM) compared with a mixture of pseudomonas-
lipopolysaccharide-reactive Fab and F(ab')2 fragments generated by pseudomonas
elastase (uptake 15.4% +/- 0.8% SEM, p less than 0.001). Hydrolyzed CF
IgG antibodies consistently resulted in a level of bacterial uptake less than that of
normal saline negative controls (NS): (
at 10 minutes, NS 26.6% vs CF 16.8%, p less than 0.05; at 75 minutes, NS 28.2% vs CF 15.4%, p less than 0.01. This suggests that the immune
polypeptides are active inhibitors of the essential neutrophil phagocyte-bacterial cell interaction. Intact immune
IgG reversed the defect in opsonophagocytosis. When intact
IgG was mixed with
IgG fragments the phagocytic rates increased directly with increasing amounts of intact
IgG. We conclude that the
elastase exoproduct secreted by Pseudomonas aeruginosa is capable of cleaving
IgG into functionally important fragments that inhibit bacterial uptake. Furthermore, this inhibition can be overcome by increasing amounts of a commercially available preparation of intact immune
IgG.(ABSTRACT TRUNCATED AT 250 WORDS)