Helper cells (Leu-3a+) carry the specificity of nickel sensitivity reaction in vitro in humans.

Suppressor and helper T-cell functions were studied in nickel (6.25 micrograms/ml)-induced 7-day blast transformation reaction in vitro. This was done in cocultures of 5 pairs of HLA-identical siblings; one of the siblings was nickel-sensitive and the other healthy. Suppressor and helper cells were isolated by panning, using monoclonal antibodies Leu-2a and Leu-3a. Helper cells from the nickel-sensitive siblings were obligatory for the blast transformation reaction to occur. Helper cells from the healthy sibling were not able to elicit blast transformation. Suppressor cells from nickel-sensitive and healthy subjects did not functionally differ from each other in their ability to support nickel-induced blast transformation, but the presence of suppressor cells was essential for the blast transformation reaction to occur. Proportional amounts of suppressor, helper, and Ia-antigen (Leu-10 positive)-bearing cells and monocytes (Leu-3M positive) were determined by avidin-biotin-peroxidase complex immunoperoxidase method before culturing the cells and on the seventh day of nickel-induced blast transformation culture. This was done in 6 pairs of unrelated nickel-sensitive and healthy subjects. Amounts of neither suppressor cells nor monocytes increased during the culture. Helper cells increased in both groups (p less than 0.0025). Ia-antigen bearing cells increased only in the cultures of nickel-sensitive subjects (p less than 0.0025). In conclusion, helper T cells seem to carry the specificity of nickel-induced blast transformation reaction, but suppressor T cells are also needed. Unresponsiveness to nickel is not due to specific suppressor T cells.