Binding of alpha2-macroglobulin to collagen type I: modification of collagen matrix by alpha2-macroglobulin induces the enhancement of macrophage migration.

Alpha2-macroglobulin (a2M) secreted by tissue macrophages and fibroblasts functions in the environment of extracellular matrix macromolecules. We supposed that it may interact with these molecules and change the properties of extracellular matrix. Modified variant of ELISA was used to prove the direct binding of human a2M to collagen. Native and transformed by plasmin a2M, as well as plasmin, used as the control, were labeled by biotin. It has been found that the transformed, but not the native a2M form binds to type I collagen molecules: K(d)=(1.168 +/- 1.14) x 10(-11) M. The data obtained give a strong evidence of high power of the interaction between a2M and type I collagen: practically no reverse dissociation may be seen for such a binding. The modification of three-dimensional collagen matrix by binding to the transformed a2M resulted in the enhancement of migration of macrophages, carrying the receptors for a2M, but not splenocytes that lack for such receptors. Our results allow to suggest that a2M may be one of the components of extracellular matrix, and may change the properties of microenvironment for immunocompetent cells during the processes of inflammation, reparation and tumor invasion.

Alpha2-Macroglobulin Modulates Interactions between Lymphocytes and Fibroblasts.

The aim of the present study was to evaluate the influence of apha2-macroglobulin (alpha(2)M) on lymphocyte adhesion to fibroblasts. Peripheral blood lymphocytes from healthy donors and two fibroblast lines (human diploid embryo fibroblasts M-19 and mouse transformed fibroblasts L929) were used in the experiments. alpha(2)M treatment of fibroblast monolayer appeared to result in the enhancement of lymphocyte adhesion to fibroblasts. The number of attached lymphocytes was increased by 2-2.5 times. It should be noted that the effect of alpha(2)M didn't depend on the conformational molecule changes, since either native or methylamine or plasmin transformed alpha(2)M approximately at the same fashion increased the lymphocyte adhesion to both allogeneic and xenogeneic fibroblasts. B lymphocytes were predominant cells that were attached to fibroblast monolayer without alpha(2)M treatment. However the percentage of adherent T lymphocytes was increased substantially after the fibroblast monolayer treatment by alpha(2)M. Subpopulation analysis has shown that fibroblast pretreatment by alpha(2)M didn't result in a selective adhesion of CD4(+) or CD8(+) T lymphocytes, but increased the adhesiveness for both T lymphocyte subpopulations. The data obtained demonstrate that besides its participation in the processes of fibroblast adhesion alpha(2)M is capable to modify the contact interaction of these cells with lymphocytes that may have an influence on the functional consequences of this process.

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.