Nd were processed for assays or cryopreservation of blood components within 28 hours of phlebotomy. Lymphocyte proliferative responses to whole protein antigens were measured using a membrane dye dilution methodology adapted from da Silva et al [15]. PBMC were treated with 8M PKH26, a fluorescent membrane dye, using the manufacturer's protocol (Sigma Chemical Co.), then cultured in duplicate at 2