Table 4.

Proliferative responses of P6-specific T cell clones.

	In vitro proliferative responses					% of cloned T cells secreting interferon gamma (IFNγ) assessed by flow cytometry intracellular staining
Clone # (5 × 104 cells)	MediumCPM	Peptide 6		Purified protein derivative (PPD)		T cell clones stimulated with
		CPM	Stimulation index (SI)	CPM	SI	PPD	Peptide 6
P6-6	17	47	1.8
P6-9	27	289	2.8
P6-11	27	1,562	56.2	164	1.1	3.31	80.25
P6-12	27	2,231	80.8	314	10.6
P6-13	24	964	39.2
P6-14	26	1,205	45.3
P6-15	15	426	26.8
P6-24	14	2,090	148.3
P6-25	37	65	0.8

5 × 10⁴ P6-specific T cell clones were cultured with or without 50 μg/ml of P6 together with 5 × 10⁴ irradiated spleen cells as APC in 96-well culture plates. Some cultures contained 20 μg/ml of PPD as negative control. Sixteen hours before termination of cultures, 1 μCi of tritiated thymidine (³H) was added to each well. The results were expressed as mean counts per minute and as stimulation indexes. The clonality of clone P6-11 was assessed by intracellular staining for IFNγ. P6-11 was stimulated in culture for 48 h with either PPD or Peptide 6 and 10⁶ irradiated spleen cells as antigen-presenting cells, some of which might have survived the 48-h culture and appeared as non-IFNγ-secreting cells.

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