Cross‐talk between Vβ8+ and γδ+ T lymphocytes in contact sensitivity

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Abstract
We have previously reported that T lymphocytes proliferating in vitro to the hapten trinitrochlorobenzene (TNCB) exhibit a very restricted Vβ gene usage and response to TNCB is limited to T-cell receptors (TCR) composed of Vβ8.2 in combination with Vα3.2, Vα8 and Vα10. This paper investigates the role played by T lymphocytes expressing the Vβ8.2 gene segment in the contact sensitivity (CS) reaction to TNCB in the intact mouse and in its passive transfer into naive recipient mice. Mice injected with monoclonal antibodies to Vβ8 are unable to develop CS upon immunization with TNCB and 4-day TNCB-immune lymph node cells from mice that had been depleted in vivo or in vitro of Vβ8+ T lymphocytes fail to transfer CS. However, when separated Vβ8+ and Vβ8− cells were used for passive transfer, it was found that Vβ8+ T lymphocytes failed to transfer CS when given alone to recipient mice and a Vβ8− population was absolutely required. Further analysis revealed that within the Vβ8− population, T lymphocytes expressing the γδ TCR were fundamental to allow transfer of the CS reaction. These γδ cells were found to be antigen non-specific, genetically unrestricted and to rearrange the Vγ3 gene segment. This indicates that transfer of the CS reaction requires cross-talk between Vβ8+ and γδ+ T lymphocytes, thus confirming our previous results obtained using TNCB-specific T-cell lines. Time–course experiments showed that Vβ8+ lymphocytes taken 4–24 days after immunization with TNCB were able to proliferate and produce interleukin-2 (IL-2) in response to the specific antigen in vitro. Similar time–course experiments were then undertaken using the passive transfer of the CS reaction system. The results obtained confirm that TNCB-specific Vβ8+ T lymphocytes are present in the lymph nodes of immunized mice from day 4 to day 24, and reveal that γδ+ T lymphocytes are active for a very short period of time, i.e. days 4 and 5 after immunization. In fact, TNCB-specific Vβ8+ cells are able to transfer CS when taken 4–24 days after immunization, providing the accompanying Vβ8− or γδ+ T lymphocytes are obtained 4 days after immunization. In contrast, injection of Vβ8+ T lymphocytes together with Vβ8− or γδ+ T lymphocytes that had been taken 2 or 6 days after immunization, failed to transfer significant CS into recipient mice. Taken together, our results confirm that cross-talk between Vβ8+ and γδ+ T lymphocytes is necessary for full development of the CS reaction and may explain why the CS reaction in the intact mouse lasts up to 21 days after immunization while the ability of immune lymph node cells to transfer CS is limited to days 4 and 5 after immunization.