Table 2.

Results of regression analyses for predicting natural killer (NK) cell response to recombinant interferon gamma (rIFN γ) across five effector-to-target cell (E:T) ratios

	Dependent variable: NK cell response to rIFN γ at E:T ratios
	50:1	25:1	12.5:1	6.25:1	3.125:1
Model A, R2A*	.025	.097	.080	.138	.124
Model B†
R2B	.041	.151	.197	.257	.208
R2B–A‡	.016	.054	.117	.119	.084
βStress§	−.128	−.244	−.358	−.358	−.301
t	−1.104	−2.190	−3.203	−3.084	−2.083
df∥	82	81	74	65	46
P	.274	.032	.002	.004	.044
Model C¶
R2C	.015	.077	.149	.149	.088
t	−1.128	−2.586	−3.581	−3.343	−2.080
df∥	82	81	74	65	46
P	.264	.012	.002	.002	.044

^*Model A includes the control predictors of age, stage, and days since surgery for the immune outcome, NK cell response. The R²_A is the total variance in NK cell response explained by these three predictors.

^†Model B includes model A control variables plus the stress predictor (i.e., Impact of Event Scale [IES] score) for the immune outcome, NK cell response. The R²_B is the totla variance in NK cell response explained by the three control predictors and the stress predictor.

^‡R²_B–A is the increment in variance due to stress only (i.e., variance beyond that explainde by the control predictors) in predicting the NK cell response.

^§β_Stress is the standardized regression beta (β) for the stress variable in model B. It indicates the magnitude and direction of the influence (negative) of stress onthe immune outcome.

^∥df refers to the degrees of freedom in model B.

^¶Model C includes stress as the only predictor of the immune outcome, NK cell response. The R²_C is the total variance in NK cell response explained by stress; this model provides the simple association between psychologic stress and immune function.