Table II.

Comparison of IFN-γ secreting cells in PBMC before and after challenge

	No. SFC per 10⁶ PBMC from animals in the following group^a
	Immunized				Control
Antigen	3892	3937	3943	3959	3962	3989
Pre-challenge^b	128	377	833	521	20	−97
Post-challenge^c
2 wk	179	163	827	683	91	5
4 wk	290	71	17	−18	−15	2
6 wk	84	−23	−19	−55	94	−25
9-12 wk	180	17	104	−72	−79	−260

Cryopreserved PBMC from immunized or control animals were stimulated in triplicate wells for 40 hr with 1.0 μg/ml of F2-5 peptide (PBMC) or negative control RAP-1 P2 peptide. Results are presented as the mean number of SFC per 10⁶ PBMC after subtracting the response to negative control peptide. Significantly greater responses to F2-5 peptide are indicated in bold, determined by a Student’s one-tailed paired t-test where P<0.05.

Pre-challenge PBMC were obtained the day of challenge, except for animal 3943, where PBMC were obtained 3 wk before challenge. The response to F2-5 had too many spots to count so the no. SFC was estimated at 600 per 5 × 10⁵ cells/well.

PBMC were obtained from animals euthanized between 9-12 weeks post challenge.