We have recently found that antibodies to L-selectin, the homing receptor on neutrophils, are as effective as those to β2-integrin at blocking formyl peptide-stimulated aggregation. Therefore, we investigated the requirements for expression of L-selectin and β2-integrin on adjacent cells during aggregation. Fluorescence flow cytometry allowed characterization of aggregates on the basis of size and color, as well as antibody binding to these two adhesive molecules. Formyl peptide-stimulated aggregate formation was measured for individual populations fluorescently labeled red (LDS-751) or green (CD44-FITC), and interpopulation red-green cell conjugates. Blocking either the β2-integrin or L-selectin adhesive epitope with monoclonal antibody on individual cell populations resulted in an ≃50% reduction in two-color aggregation as compared with that in unblocked samples. Shedding the L-selectin on a cell population by preincubation with complexes of lipopolysaccharide and its plasma membrane binding protein also decreased aggregation to a control population by ≃50%. We examined the aggregation of neutrophils from patients genetically deficient in β2-integrin and clinically leukocyte adhesion deficient (LAD). LAD adhesion to normal neutrophils was dependent on the expression of L-selectin on LAD cells and β2-integrin on normal cells. Thus, the minimum requirement for adhesion between two mixed populations of neutrophils was that one population expressed the β2-integrin and the other expressed the L-selectin adhesive epitope.
|Original language||English (US)|
|Number of pages||10|
|State||Published - 1993|
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