A novel monoclonal antibody of human stem cell factor inhibits umbilical cord blood stem cell ex vivo expansion

Table 1 Inhibitory effects of mAb 23C8 on CD34 ⁺ cell ex vivo expansion

Additions		mAb:SCF molar ratio	MNC count at day 7 (×10⁴)	CD34⁺ cells at day 7 (% total MNC)	CD34⁺ expansion index
SCF	Anti-hrSCF
+ (reference)^a	None	0	17.50 ± 1.50	31.44 ± 1.68	6.50 ± 0.87^#
None^b	None	0	5.00 ± 0.50	31.65 ± 0.50	1.87 ± 0.21*
+	Buffer only^c	0	17.83 ± 0.58	29.12 ± 2.06	6.11 ± 0.41^#
+	+	0.25	9.90 ± 0.93	31.64 ± 2.38	3.67 ± 0.09*^#
+	+	0.50	5.00 ± 1.00	30.66 ± 0.39	1.80 ± 0.34*
+	+	1.0	4.50 ± 1.00	26.16 ± 1.27	1.39 ± 0.35*
+	+	2.0	4.50 ± 1.32	28.52 ± 4.41	1.52 ± 0.50*
+	+	5.0	4.67 ± 1.44	29.95 ± 4.00	1.60 ± 0.33*
+	+	10	4.25 ± 0.43	28.38 ± 1.71	1.43 ± 0.22*

Each well was added with umbilical cord blood MNC (~7.3 × 10⁴, containing 11.63% CD34⁺ cells), in 0.5 ml of STEM PRO®-34SFM medium containing 50 ng/ml rhTPO and 200 ng/ml rhFL on day 1. Additional reagents were added to various groups, as indicated, including 200 ng/ml reference rhSCF or rhSCF produced in-house, and mAb buffer alone or anti-rhSCF mAb added at different amounts. Cells were cultured at 37°C, with humidified air containing 5% CO₂, for 7 days. Culture medium was replenished on day 3. Data represent means ± SD, n = 3. CD34⁺ expansion index is defined as the fold increase [(after expansion)/(before expansion)] in total CD34⁺ cell count.
^aPositive control.
^bNegative control.
^cVehicle control.
*, P < 0.05, compared with vehicle control and positive control.
^#, P < 0.05, compared with negative control.

ISSN: 1756-8722