Interferon-gamma responses to Plasmodium falciparum liver-stage antigen-1 and merozoite-surface protein-1 increase with age in children in a malaria holoendemic area of western Kenya

Table 4 Frequencies and geometric mean levels of IFN-γ responses to PHA, LSA-1 and MSP-1 peptides by age.

Condition	PHA		MSP-1 (aa 20–39)		LSA-1, T3
Age (months)	No. pos./Tot. (%)^a	Geo. mean (range)^b	No. pos./Tot (%)	Geo. mean (range)	No. pos./Tot (%)	Geo. mean (range)
0–12	11/11 (100)	2481.8 (164.9–6206.5)	1/10 (10.0)	12.2 (0–105.5)	0/9 (0.0)	0 (0–0.0)
13–24	12/12 (100)	1859.7 (95.1–3635.4)	1/10 (10.0)	124.6 (0–1245.9)	1/9 (11.1)	71.7 (0–645.2)
25–36	13/13 (100)	2875.7 (547.1–6891.6)	3/11 (27.3)	137.7 (0–1003.4)	4/11 (36.4)	68.6 (0–443.2)
37–48	12/12 (100)	2294.1 (99.8–4254.1)	4/10 (40.0)	203.7 (0–1097)	4/10 (40.0)	217.9 (0–983.5)
P	NS^c	NS^d	0.070	NS	0.019	NS

^a A positive response was defined as any response ≥ 20 pg/ml above that of unstimulated cell culture supernatants. ^b Geometric mean cytokine levels in pg/ml. ^c NS= not significant. P < 0.05 considered significant, as determined by χ² test for trend across age groups. ^d P < 0.05 was considered significant as determined by analysis of variance of log-transformed values across age groups.

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