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).