We developed a method for production of antigen-specific, H-2-restricted T cell hybrids. The tumor cell partner in the fusions was itself a T cell hybrid, FS6-14.13.AG2 (or its derivatives), which could be induced to produce the growth factor, interleukin-2 (IL-2), in response to a challenge with concanavalin A, but had no known antigen specificity. The normal T cell partner in the fusions was a population of lymph node T cell blasts that had been highly enriched in antigen-specific, H-2-restricted T cells by in vivo immunization, followed by in vitro challenge with antigen and clonal expansion in IL-2-containing medium. These fusions produced hybrids that grew constitutively in culture. A sizable proportion of the hybrids demonstrated the ability to produce IL-2 in response to a challenge with specific antigen presented by irradiated spleen cells of the appropriate H-2 type.

Four cloned antigen/H-2-specific hybrid lines were produced. AO-40.10 responded to chicken ovalbumin (OVA) when presented by I-A(k)-bearing cells. DC1.18.3 responded to the apo form of beef cytochrome c when presented with I-A(d). AODK-10.4 responded to keyhole limpet hemocyanin (KLH) presented with I-A (d). AODK-1.16 also responded to KLH presented by a product of the I region of H-2(d), but the data were consistent with either a product of the I-J-I-E(d) region or a combinatorial molecule with elements from both I-A(d) and I-E(d)/I-C(d). Coincidentally, AO-40.10 was shown to have an unexpected alloreactivity with a product of H-2(b) mapping to the K-I-A region. These hybrids should prove invaluable as sources of monoclonal material for the study of the receptor(s) on T cells with H-2-restricted antigen specificities.

We also generated T cell hybrids with two antigen/H-2 specificities by fusing an azaguanine-resistant clone of AO-40.10 to normal T cells with a different antigen/H-2 specificity. Many of the hybrids retained reactivity to OVA plus H-2(a) and to the second antigen/H-2 combination. None reacted to either OVA plus the second H-2 type or to the second antigen plus H-2(a).

One of these hybrids was successfully cloned to produce the line AOFK- 11.11.1. It retained the ability to recognize OVA plus I-A(k) inherited from one parent, and KLH plus IA(f) inherited from the other. It did not recognize OVA plus IA(f) or KLH plus I-A(k).

These results have some bearing on models describing the nature of T cell receptors for antigen recognized in association with H-2 products. They do not support models in which antigen and H-2 are recognized separately by two independent T cell receptors.

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