Subsets of null and γδ T-cell receptor+ T lymphocytes in the blood of young pigs identified by specific monoclonal antibodies.

Rat monoclonal antibodies (mAb) against isolated pig Null T cells were derived using a novel twocolour cytofluorometric assay. One (MAC320) identified all blood CD2^- sIg^- 'Null' cells (present at up to ∼6 × 10⁶/ml). Another type (MAC319 and MAC318) identified a subset comprising ∼60% or ∼30% of the Null cell population. This percentage appears genetically determined. This subset partially overlapped with a γδ T-cell receptor⁺ (TcR⁺) population which consisted of ∼40% of Null T cells. The antibodies did not react with other leucocyte or lymphocyte populations. In non-reducing conditions, MAC320 precipitated two molecules at ∼270,000-280,000 MW in SDS-PAGE; the larger of which was also precipitated by MAC319 (and MAC318, which binds to the same epitope). Under reducing conditions, MAC320 immunoprecipitated two or three polypeptide chains at ∼130,000-160,000 MW; MAC319 precipitated only the largest of these polypeptides, The large MAC319⁺ MAC320⁺ molecule on one subset is removed by bromelain treatment; the smaller MAC319^- MAC320⁺ molecule on the remaining Null cells is not bromelain sensitive. Several properties of this new antigen complex specific to pig Null T cells show that it is distinct from the ruminant T19 complex. [ABSTRACT FROM AUTHOR]