Effect of aggregated IgG on mononuclear and polymorphonuclear cell cooperation

The leukocyte adherence inhibition (LAI) test was used to determine the response of different leukocyte subpopulations in rheumatoid arthritis (RA) patients and normal donors to heat-aggregated gammaglobulins (HAGGs). The adherence of polymorphonuclear cells of (PMNs) could be inhibited either directly by high concentrations of HAGGs or indirectly by soluble factors secreted by RA mononuclear cells incubated with low amounts of HAGGs. The stimulatory site of the IgG was located on the Fc fragment. Since the LAI reaction was also observed with material recovered from rheumatoid synovial fluid, tissue, and nodules, these results could have clinical relevance in RA.