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Monoclonal antibody-defined functional epitopes on the adhesion-promoting glycoprotein complex (CDw18) of human
Abstract:
We have evaluated the functional and immunochemical activities of three monoclonal antibodies (MoAbs) minimally reactive with adherence-defective neutrophils (PMN) from a patient with recurrent bacterial infections. In studies with normal PMN, MoAbs OKM1 and 60.1 both precipitate the same 165kd alpha-subunit (alpha M) within an alpha-beta heterodimer complex (CD11). The CD11 complex is part of a larger complex composed of four glycoproteins (CDw18) precipitated by MoAb 60.3, with properties suggesting that the CDw18 complex is equivalent to the Mac-1, LFA-1, p150, 95 glycoprotein family implicated in adherence-dependent leukocyte functions. PMN adherence to endothelium, spreading on surfaces, aggregation, and phagocytosis of zymosan particles were all inhibited in a dose-dependent fashion by MoAb 60.1 (analogous to previous studies with MoAb 60.3) while MoAb OKM1 had no effect. These findings unify previously disparate observations and suggest that a functionally active site on the adherence promoting glycoprotein complexes CD11 and CDw18 is distant from the alpha M epitope recognized by MoAb OKM1 but closely associated with the alpha M epitope recognized by MoAb 60.1 and the beta-epitope (or epitope created by alpha-beta quaternary structure) recognized by MoAb 60.3.
Insights
Monoclonal antibodies targeting CD11 and CDw18 glycoproteins on neutrophils can inhibit adherence-dependent functions. Antibody 60.1 effectively blocks these functions, unlike OKM1, indicating distinct epitope interactions.
Area of Science:
- Immunology
- Cell Biology
- Molecular Medicine
Background:
- Neutrophil adherence is crucial for immune responses.
- Defects in neutrophil adherence lead to recurrent bacterial infections.
- Monoclonal antibodies (MoAbs) are tools to study cell surface proteins.
Purpose of the Study:
- To evaluate the functional and immunochemical activities of MoAbs against adherence-defective neutrophils.
- To investigate the role of CD11 and CDw18 glycoprotein complexes in neutrophil adherence.
Main Methods:
- Precipitation assays using MoAbs OKM1, 60.1, and 60.3.
- Functional assays including neutrophil adherence, spreading, aggregation, and phagocytosis.
- Analysis of glycoprotein complexes (CD11 and CDw18) on normal neutrophils.
Main Results:
- MoAbs OKM1 and 60.1 precipitate the alpha M subunit of the CD11 complex.
- MoAb 60.3 precipitates the CDw18 complex, part of the Mac-1/LFA-1 family.
- MoAb 60.1 inhibited neutrophil adherence, spreading, aggregation, and phagocytosis in a dose-dependent manner.
- MoAb OKM1 showed no effect on these functions.
Conclusions:
- The functionally active site for adherence is distinct from the OKM1 epitope on the CD11 alpha M subunit.
- The active site is associated with the 60.1 epitope on the alpha M subunit and the beta-epitope recognized by 60.3.
- These findings clarify the structure-function relationship of CD11/CDw18 in neutrophil adherence.