Comparison between Nu/Nu and normal BALB/c T-helper activity in anti-hapten and anti-carrier responses.

Nu/nu BALB/c mount a primary in vivo anti-TNP response to T-dependent TNP-antigens in the range of normal BALB/c mice. However, the response against the carrier (horse red blood cells, HRBC) was in the magnitude of about 5% as compared to normal BALB/c mice. Neither against the hapten, nor against the carrier a secondary response was observed. It could be shown by in vitro experiments that nu/nu contain a small population of TNP specific as well as HRBC specific T-helper (THTNP, THHRBC) cells. But even within the small nu/nu T-cell population, TH cells are less frequent than in T-cell populations of normal mice. Furthermore, the difference in help between nu/nu and normal BALB/c was more pronounced with respect to the anti-HRBC than the anti-TNP response. These observations could explain the lack of a secondary in vivo response being due to the low number of TH cells and the apparent in vivo unresponsiveness against HRBC as a consequence of the low frequency of THHRBC.