Hemolytic Complement Activity Assay
To assess if diet macronutrient content (experiment 1) and social cues of disease (experiment 2) influenced the complement pathway, we conducted a CH50 complement assay that measures the ability of proteins in the plasma to lyse sheep red blood cells (MP Biomedicals, Cat#55876). We measured complement activity following the methods outlined in Sinclair and Lochmiller (2000). Briefly, we ran duplicate 80 μl samples of 1:20 and 1:40 plasma dilutions. Hemolytic complement activity was expressed as CH50 units/ml plasma, where one CH50 unit signifies the reciprocal of the dilution of plasma needed to lyse 50% of the sheep red blood cells (French et al. 2010).