ISOLATED HAPTEN-BINDING RECEPTORS OF SENSITIZED LYMPHOCYTES II. Receptors from Nylon Wool-Enriched Rabbit T Lymphocytes Lack Serological Determinants of Immunoglobulin Constant Domains but Carry the A Locus Allotypic Markers* BY ULRICH KRAWINKEL,$ MATTHIAS CRAMER, ROSE G. MAGE,

In the preceding paper I a class of hapten-binding lymphocyte receptor molecules was described which lack detectable serological determinants of conventional immunoglobufin constant domains but appear to carry heavy chain variable portions. These receptor molecules which we call the anti-lgfraction as well as receptor molecules expressing class-specific imunoglobulin determinants-the so-called anti-lg + fraction-are isolated from hapten-sensitized mouse lymphocytes by means of an immunosorbent. The cells are specifically absorbed to haptenated nylon mesh at 4°C (1, 2) and released by temperature shift (2). Subsequently hapten-binding material is eluted from the nylon mesh (3-5). The material can be titrated in the haptenated phage inactivation (HPI) 2 assay (3-5). I The anti-Ig + fraction was shown to correlate with the B-cell fraction in the cell input whereas the anti-lgfraction correlated with the T-cell fraction. It is therefore attractive to think that the anti-lg + fraction represents B-cell receptors for antigen whereas the anti-lgfraction consists of antigen receptors of T lymphocytes. This interpretation is in accord with a large body of experimental work (3-6). I