Pregnancy-Associated Plasma Protein-A, Alpha-2-Macroglobulin, Pregnancy Zone Protein and Their Complexes with IgG in Sera of Healthy Non-Pregnant and Pregnant Woman, and Patients with Breast Cancer.

The purpose of this study was to measure alpha-2-macroglobulin-IgG (alpha(2)-MG-IgG), pregnancy zone protein-IgG (PZP-IgG) and pregnancy-associated plasma protein-A-IgG (PAPP-A-IgG) complex concentrations in serum in comparison with total alpha(2)-MG, PZP and PAPP-A concentration, and to determine the possible role of such complexes. Serum samples were obtained from 20 healthy women, 30 patients with verified metastatic breast cancer (stage III-IV) before the treatment and 40 healthy women with normal pregnancy (I-III trimester in dynamics). The serum concentrations of alpha(2)-MG-IgG, PZP-IgG and PAPP-A-IgG complexes were measured by ELISA. It has been shown that the immune complexes of the major proteinase inhibitors such as alpha(2)-MG, PZP and PAPP-A with IgG may be found at minor concentration in blood of both the healthy women and patients with breast cancer. On the other hand, their physiological functions in organism are absolutely different. We suggest that alpha(2)-MG-IgG and PZP-IgG complexes can serve as immunoregulatory signal molecules. Thus, after calculation of a molar ratio, less than 1% of alpha(2)-MG and PZP were marked by IgG. On the contrary, one PAPP-A molecule can bind to 10-15 IgG molecules in samples of control non-pregnant women and breast cancer patients. Such a kind of binding gives an evidence in favor of alternative way of utilization and degradation of PAPP-A by monocyte-macrophages through a Fc-receptor.