Modulation by Centrifugation of Cell Susceptibility to Chlamydia1 Infection

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Abstract
Enhancement of chlamydial [Chlamydia psittaci] infection of [human synovial McCoy] cell monolayers by centrifugation depended on induced cell surface changes. Evidence for this came from analysis of 2 forms of organism attachment which take place during centrifugation. In productive binding, organisms attached to cells and then entered and infected them. In unproductive binding, organisms became attached to cells but were not ingested. These organisms could be stripped from the cells by treatment with trypsin and could then infect fresh monolayers. Measurement of attachment kinetics during centrifugation showed that cells passed through 3 different susceptibility states. Only productive binding occurred in the first 20 min; cells then entered a refractory state during which no attachment took place. At about 45 min, attachment recommenced but this allowed only unproductive binding. Induced movement of cell surface structures may enhance infection by promoting specific or non-specific interactions. Failure of ingestion may result from insufficient cell receptors for circumferential binding of the whole chlamydial surface so that engulfment cannot take place.