TABLE 2.

Cytokine production by HeLa cells after Y. enterocolitica infection

Cytokine	Concn (pg/ml)a
	Controlb				Y. enterocolitica
	SNc		Lysated		SN		Lysate
	4–6 h	24 h	4 h	24 h	4–6 h	24 h	4 h	24 h
IL-8	29 ± 2.4	218 ± 0.0	<5	<5	890 ± 10.3*	897 ± 83.8*	<5	<5
TNF-α	<15	<15	<15	<15	<15	<15	<15	<15
IL-1α	<0.5	<0.5	<0.5	<0.5	<0.5	<0.5	107 ± 12.5*	52 ± 27.5*
IL-1β	<1	<1	<1	<1	<1	<1	26 ± 8.6*	4 ± 5.4*
MCP-1	<10	141 ± 56.3	<10	<10	304 ± 18.3*	817 ± 32.5*	26 ± 12.8*	<10
GM-CSF	<2.8	ND	<2.8	ND	137 ± 8.7*	ND	<2.8	ND

^aMean ± standard deviation of triplicate samples from a representative experiment. *, statistically significant difference at P < 0.05. ND, not determined. 

^bHeLa cells were exposed to medium (control) or Y. enterocolitica pYV⁻ (MOI of 150) for 1 h. Cells were then washed with PBS, and medium containing gentamicin was added to kill extracellular bacteria. 

^cCytokine concentration in culture supernatant (SN) was measured by ELISA at the indicated times postinfection. 

^dCells were lysed as described in Materials and Methods after the indicated time points to determine intracellular cytokine concentrations by ELISA.