B cell helper factors. I. Requirement for both interleukin 2 and another 40,000 mol wt factor.
Leibson HJ, Marrack P, Kappler JW. B cell helper factors. I. Requirement for both interleukin 2 and another 40,000 mol wt factor. J Exp Med. 1981 Nov 01; 154(5):1681-93.