TABLE 1.

CTLA-4Ig blocks the production of cytokines in response to L. major^a

Treatment	1st stimulation		2nd stimulation
	IFN-γ	IL-5	IFN-γ	IL-5
L. major	77 ± 10	14 ± 2	134 ± 11	18 ± 3
L. major + CTLA-4Ig	<10	<10	<10	<10
L. major + control Ig	90 ± 17	14 ± 1	142 ± 6	17 ± 2

^aPBL were stimulated with autologous L. major-infected adherent cells (macrophages) in the presence of CTLA-4Ig or control Ig. After 7 days (primary stimulation), supernatants and blast cells were harvested. Blast cells were restimulated using autologous L. major-infected adherent cells without additional CTLA-4Ig. Supernatants were harvested after 48 h (secondary stimulation). Cytokine concentrations in culture supernatants were determined by ELISA. Values are presented as mean ± standard error for three donors, with background cytokine levels subtracted. Cytokine levels for PBL cultured with uninfected adherent cells (background levels) ranged <10 to 35 pg/ml for IFN-γ and <2.0 to 5.5 pg/ml for IL-5.