TABLE 2.

DT-specific proliferation of lymph node cells from DT-immunized huPBL-SCID mice^a

Group	DT stimulation	[3H]thymidine uptake (cpm)b
PBLs	−	2,565 ± 168
	+	9,086 ± 272
PBLs plus rhPRL	−	1,939 ± 203
	+	14,843 ± 804*

^ahuPBL-SCID mice were created and then immunized with DT as described in the legend to Fig. 1. Ten micrograms of rhPRL or HBSS was injected i.p. every other day for a total of 20 days. On day 28 after huPBL transfer, lymph nodes (axillary, inguinal, and mesenteric) were harvested, and the cell suspension was used in a DT-specific proliferation assay in vitro. DT (10 ng/ml) and lymph node cells (1 × 10⁶/200 μl/well) were added to flat-bottomed 96-well plates (Costar). Five days later, proliferation was assayed by pulsing cells with 1 mCi (3.7 × 10⁴ Bq) of [³H]thymidine (6.7 Ci/mmol; New England Nuclear, Boston, MA) for 8 h and harvesting them with a MASH II apparatus (Microbiological Associates, Bethesda, MD). Student's t test was performed to determine statistical differences.

^bData are means ± SD. *, P < 0.01, comparing PBL-plus-hPRL group with PBL group in response to DT stimulation.