TABLE 4.

Frequency of IFN-γ-secreting cells in PBMCs and spleen lymphocytes over the course of infection in A. marginale Florida-infected cattle^a

Animal, cell or organ, and day p.i.	Mean no. of SFCs per 106 lymphocytes in response to:
	Medium	A. marginale
33875, PBMC
0	19	79
18	226	180
27	82	52
76	110	33
104	144	110
33901, PBMC
0	4	6
6	5	12
18	40	15
27	52	37
32	49	22
76	102	65
104	118	91
33875, spleen
0	28	86
36	600	600
55	121	600
76	369	600
98	254	89
33901, spleen
0	20	12
25	7	9
48	65	55
55	94	427
76	48	96
98	91	95
104	8	28

^aCryopreserved PBMCs were thawed and used simultaneously in the same assay to reduce assay-to-assay variation. IFN-γ ELISPOT assays were performed in triplicate with 1 × 10⁶ cells per well with either medium or 15 μg/ml A. marginale Florida strain homogenate for 48 h at 37°C. Results are presented as the mean numbers of SFCs. p.i., postinfection. For values of ≥600 SFCs (too numerous to count), a statistical comparison was not performed.