Despite the apparent health benefits of social relationships, some studies indicate that larger social networks can be associated with greater vulnerability to infectious disease, particularly if stressors are also present. Two possibilities for such effects are, first, that more social contacts lead to more negative affect and social conflict during stressors, or second, that maintaining more social contacts is an energetically costly activity, and ecologically motivated immunosuppression is one means of providing energy to maintain social resources. First-year law students (N=76) completed questionnaires and had delayed-type hypersensitivity skin tests at five time points during their first 6 months of law school. Both moving away from home and a smaller social network associated with larger DTH responses (both p<0.05) across all time points. However, negative affect, either broadly defined or as specific affects (hostility, sadness, guilt), did not mediate social network effects, suggesting that negative affect and social conflict are less plausible explanations than ecological immunosuppression. Ecological models would predict that temporary immunosuppression is less harmful to health in the long run than loss of social resources.