Panel A: EPO-mediated suppression is blocked by 1-MA. C57BL/6J PerC cells were cultured with (left to right) anti-CD3, anti-CD3 + 1-MA, anti- CD3 + 100 ng/ml EPO, anti-CD3 + 100 ng/ml EPO + 1-MA. Panel B: EPO effect is absent in IFNγR−/− PerC cells. Left to right, C57BL/6J PerC cells with anti-CD3, anti-CD3 + 100 ng/ml EPO; IFNγR−/−cells with anti- CD3, anti-CD3 + 100 ng/ml EPO. Panel C: EPO effect is absent in iNOS−/− PerC cells. Left to right, C57BL/6J PerC cells with anti-CD3, anti-CD3 + 100 ng/ml EPO; iNOS−/−cells with anti-CD3, anti-CD3 + 100 ng/ml EPO.