Table 1.

Affinities and maximal binding of CCR5 MAbs to CD4⁺ T cells and U87-CD4-CCR5 cells

MAb	Isotype	Epitopea	CD4+ T cellsb		U87-CD4-CCR5 cellsb
			EC50 (μg/ml)	Maximal GMFI	EC50 (μg/ml)	Maximal GMFI
PA8	IgG1	NT	22 ± 9.9	44 ± 4.0	12 ± 6.7	400 ± 37
PA11	IgG1	NT	9.8 ± 6.9	410 ± 47	34 ± 11	1,500 ± 177
45502	IgG2B	NT	85 ± 19	36 ± 6.8	NA	0c
CTC5	IgG1	NT	3.6 ± 2.6	210 ± 20	19 ± 2.7	2,000 ± 80
PA10	IgG1	NT-ECL2d	>200	>2,600	215 ± 138	380 ± 106
PA14	IgG1	NT-ECL2	9.1 ± 4.1	500 ± 36	10 ± 3.6	1,300 ± 78
2D7	IgG2A	ECL2	1.5 ± 0.76	340 ± 22	1.2 ± 0.26	980 ± 26
45531	IgG2B	ECL2	6.3 ± 1.0	490 ± 12	16 ± 6.2	1,400 ± 98
45523	IgG2B	MD	31 ± 6.8	75 ± 3.6	139 ± 47	1,600 ± 209
45549	IgG2B	MD	NA	0c	40 ± 8.6	800 ± 67

^aAs defined in references 29 and 40. MD, multidomain.

^bEC₅₀ and GMFI values (±standard errors of the mean [SEM]) are based on the fitted curves generated from the data points shown in Fig. 1. EC₅₀ is the MAb concentration giving half-maximal binding. Maximal GMFI is the fitted plateau value. Therefore, it might not always be the same as the highest value reached in Fig. 1. The data were derived from one experiment of two performed for each cell type. The purified CD4⁺ T cells expressed high levels of CD4 (GMFI = 5,000). NA, not applicable.

^cNo binding detectable.

^dThe PA10 epitope was originally reported to involve both the NT and ECL2 (40), but the MAb was later shown to bind to a tyrosine-sulfated NT peptide (12). Whether ECL2 residues are also involved is not clear.