Immunosuppressive properties of electrophoretically "slow" and "fast" form alpha 2-macroglobulin. Effects on cell-mediated cytotoxicity and (allo-) antigen-induced T cell proliferation.
Lymphokine activated killer cell lysis of K562 cells was inhibited by alpha 2-macroglobulin (alpha 2M), soybean trypsin inhibitor, and alpha 1-proteinase inhibitor. In serum free medium 2 mg/ml alpha 2M suppressed target cell lysis in a 4-h cytotoxic assay with about 40%. Suppression was dose and time dependent. Cytotoxicity was unaffected by alpha 2M concentrations less than 0.25 mg/ml, and by alpha 2M added later than 1.5 h from start of assay. Pre-treatment of effector (but not of target) cells with alpha 2M was even more suppressive than the presence of alpha 2M during assay. Cell-mediated cytotoxicity was not inhibited by alpha 2M treated with methylamine or by various alpha 2M-proteinase complexes. In contrast, alpha 2M-proteinase complex as well as native alpha 2M suppressed the proliferation of Ag-activated T cells. However, methylamine-treated alpha 2M did not inhibit T cell proliferation, and suppression by alpha 2M-proteinase complex was significantly reduced after inhibition of the alpha 2M-bound proteinase. On incubation at 4 degrees C with lymphokine-activated killer cells, alpha 2M reacted with cell associated proteinases and changed from electrophoretically "slow" to "fast" form. Cell associated proteinases bound by alpha 2M showed chymotrypsin- and trypsin-like specificities and their activity surpassed activity caused by cellular leakage and secretion. The present results strongly indicate that alpha 2M mediates immunosuppression in its capacity as a proteinase inhibitor and suggest inhibition of (T)cell surface-associated proteinases as a possible mode of suppression.
Petersen
C M
CM
Department of Clinical Immunology, University Hospital of Aarhus, Denmark.
Ejlersen
E
E
Moestrup
S K
SK
Jensen
P H
PH
Sand
O
O
Sottrup-Jensen
L
L
D003601:Cytotoxicity Tests, Immunologic; D003602:Cytotoxicity, Immunologic / Q000187:drug effects*; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D007111:Immunity, Cellular / Q000187:drug effects; D007166:Immunosuppressive Agents / Q000302:isolation & purification / Q000494:pharmacology; D007519:Isoantigens / Q000276:immunology*; D007700:Kinetics; D008213:Lymphocyte Activation / Q000187:drug effects*; D046911:Macromolecular Substances; D010447:Peptide Hydrolases / Q000494:pharmacology; D011487:Protein Conformation; D012967:Sodium Dodecyl Sulfate; D013329:Structure-Activity Relationship; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*; D000511:alpha-Macroglobulins / Q000302:isolation & purification / Q000494:pharmacology
D007166:Immunosuppressive Agents; D007519:Isoantigens; D046911:Macromolecular Substances; D000511:alpha-Macroglobulins; D012967:Sodium Dodecyl Sulfate; D010447:Peptide Hydrolases