TABLE 2.

Inhibition of PHA-stimulated PBMC proliferation by S. pyogenes Manfredo CE is reversible^a

CE (μg/ml)	Uptake of [3H]thymidine (cpm)
	Washed PBMC	Unwashed PBMC
0	7,842 ± 77	6,194 ± 125
0.008	7,124 ± 144	6,627 ± 267
0.04	6,942 ± 792	7,781 ± 46
0.2	6,885 ± 122	7,691 ± 209
0.5b	8,161 ± 372	375 ± 115
1.0b	8,155 ± 224	70 ± 4
5.0b	6,913 ± 281	35 ± 4
Background	94 ± 5	69 ± 3

^aHuman PBMC (2 × 10⁶/ml) were cultured with CE at a range of concentrations in 96-well round-bottom plates. After 24 h of incubation at 37°C, PBMC from one plate were washed with RPMI 1640 plus 10 mM HEPES before addition of PHA to each well to give a final concentration of 1.0 μg/ml. PBMC in the second plate were not washed before addition of PHA. Incorporation of [³H]thymidine into the cells was determined after a further 3 days of incubation. Results show mean incorporation of radioactivity for triplicate wells ± SEM for one donor studied and are representative of values obtained from four different individuals. 

^bProliferation of unwashed PBMC was significantly inhibited (P < 0.00005) by CE at final concentrations of 0.5 μg/ml or higher. No significant inhibition was observed with washed PBMC.