Immunoglobulin levels in breast cyst fluid: apparent connection with intracystic transcortin (CBG) binding activity.

Immunoglobulin levels of the major classes of IgG, IgA and IgM have been measured by radial immunodiffusion in 74 samples of breast cyst fluid (BCF) aspirated by women with 'Gross Cystic Disease'. Appreciable levels of Ig were found in all samples. No significant correlation was observed between intra-cystic Ig levels and the corresponding levels measured on coincidental blood specimens. A significant linear correlation was found between intra-cystic Ig levels and the apparent specific binding activity for cortisol attributable to a transcortin like component (n = 30; p less than 0.05 for IgA, p less than 0.0025 for IgG; p less than 0.05 for IgM).