Table 1.

Effect of MV infection on cytokine secretion of KLH-specific T cells

Cytokine	Control	MV infection before 1° stimulation (day 0) and analysis on day 28	MV infection before 2° stimulation on day 28
IL-2	3,681 ± 4,794 cpm	2,054 ± 1,661 cpm	2,635 ± 2,507 cpm
IFN-γ	+	+	+
TNF	−	−	−

For primary (1°) stimulation, cotton rats were injected with KLH, and 4 weeks later their spleen cells were stimulated in vitro with KLH (see also Fig. 2B). After 24 h, supernatants were harvested to assay for the presence of IL-2 and TNF, and after 48 h, supernatant was harvested to assay for the presence of IFN-γ. With biological assay systems, the amount of cytokine produced by KLH-stimulated spleen cells from noninfected animals, and animals infected with MV before the primary or before the secondary (2°) stimulation were compared (7–11 animals per group). The proliferation (cpm ± SD) of the IL-2-dependent CTLL clone 3 cells was used as an assay system for IL-2. IFN-γ was tested as protection of primary cotton rat fibroblasts against infection with vesicular stomatis virus (serotype Indiana). +, Protection at a 2- to 4-fold dilution of T cell supernatants. TNF was assayed as killing of mouse fibroblast cell line L929. Although no killing was observed here, cotton rat T cells with different antigenic specificities secrete TNF measurable in this assay (data not shown).