Related Experiment Videos
Effect of piliation on interactions of Haemophilus influenzae type b with human polymorphonuclear leukocytes
Abstract:
Piliated, adherent (P+) and nonpiliated, nonadherent (P-) strains of Haemophilus influenzae type b (Hib) were compared with respect to their ability to induce polymorphonuclear leukocyte (PMN) chemiluminescence (CL) and superoxide (O2-) generation and their susceptibility to phagocytosis by PMNs. P+ strains opsonized in normal human serum (NHS) induced significantly greater CL than did P- strains (500 X 10(5) +/- 112 X 10(5) versus 242 X 10(5) +/- 65 X 10(5) total counts per 60 min; P less than 0.001) when reacted with normal PMNs. Contributions of immunoglobulin and complement to CL activity in these mixtures were shown by findings of lower overall levels of CL when hypogammaglobulinemic serum or heat-inactivated NHS was used to opsonize either P+ or P- organisms. Results obtained with mixtures of hypogammaglobulinemic plus adsorbed heat-inactivated NHS (with P+ or P- organisms) suggested a role for an antipilus antibody in the enhancement of CL by these strains. NHS-opsonized P+ strains also induced significantly greater (P less than 0.002) O2- generation than did P- strains (2.83 +/- 0.08 versus 1.94 +/- 0.14 nmol of ferricytochrome c reduced per 10 min/10(6) PMN). Comparable ingestion of P+ or P- strains opsonized in NHS by PMNs was demonstrated by a radiolabeled uptake technique and transmission electron microscopy, and primary granule release (beta-glucuronidase) was comparable during ingestion of P+ or P- strains. The basis for the observed enhanced capacity of P+ Hib to stimulate PMN oxidative metabolism as compared with P- organisms is uncertain. Possible clinical implications of these findings deserve further study.
Insights
Piliated Haemophilus influenzae type b (Hib) strains stimulate greater polymorphonuclear leukocyte (PMN) chemiluminescence and superoxide generation than nonpiliated strains. This enhanced immune response is linked to antipilus antibodies, though phagocytosis remains comparable.
Area of Science:
- Immunology
- Microbiology
- Cell Biology
Background:
- Haemophilus influenzae type b (Hib) is a significant pathogen.
- Bacterial virulence factors influence host immune responses.
- Polymorphonuclear leukocytes (PMNs) are critical in combating bacterial infections.
Purpose of the Study:
- To compare the immunomodulatory effects of piliated (P+) versus nonpiliated (P-) Hib strains on PMNs.
- To investigate the role of opsonization, complement, and antibodies in PMN activation by Hib.
- To assess the impact of pili on PMN chemiluminescence (CL) and superoxide (O2-) generation.
Main Methods:
- Comparison of P+ and P- Hib strains incubated with normal human serum (NHS) and PMNs.
- Measurement of PMN chemiluminescence (CL) and superoxide (O2-) generation.
- Opsonization experiments using hypogammaglobulinemic serum and heat-inactivated NHS.
- Assessment of bacterial uptake and primary granule release via radiolabeled techniques and electron microscopy.
Main Results:
- P+ Hib strains induced significantly higher PMN CL and O2- generation compared to P- strains when opsonized in NHS.
- Immunoglobulin and complement in NHS were crucial for CL activity.
- Antipilus antibodies appeared to enhance CL.
- Phagocytosis and primary granule release were comparable for both P+ and P- strains.
Conclusions:
- Piliated Hib strains exhibit an enhanced capacity to stimulate PMN oxidative metabolism compared to nonpiliated strains.
- The enhanced response is partly mediated by antipilus antibodies.
- Further research is needed to elucidate the precise mechanisms and clinical implications.