Inhibition of human CD4⁺ T cell proliferation by Lptn.

(A) [³H]-TdR incorporation of 1 × 10⁵cells purified CD4⁺ T cells activated with plate-bound CD3 mAb for 5 days, in the presence or absence of the following reagents: Lptn or RANTES coated at the same time as CD3 mAb, and their specific antibodies. The [³H]-TdR pulse was undertaken as described in “Materials and methods.” Results are expressed as the mean values of cpm from quadruplicate cultures, obtained from 7 independent experiments. The error bars were derived from standard deviations of the determinations. The 33 × 10³ cpm were obtained in response to CD3 and CD28 costimulation (positive control) as compared with 11.5 × 10³ cpm for CD3 alone (not shown). (B) The [³H]-TdR incorporation was measured from CD4⁺ T cells activated in the same conditions as in panel A, except for the presence of soluble instead of coated Lptn. The figure represents the mean values ± SD of 3 independent experiments. (C) The CD4⁺ T cell [³H]-TdR pulse induced by CD3 stimulation is reduced in a dose-dependent manner by Lptn. Each point of the curve represents the mean ± SD of cpm from 2 independent experiments performed in triplicate.