Detection of autologous mixed lymphocyte reaction responding cells and their precursor frequency in NZB mice

The autologous mixed lymphocyte reaction (AMLR) can be detected in older NZB mice after treatment of the responding cell population with monoclonal anti-I-A^d and complement and supplementation of the culture medium with T-cell growth factor (TCGF) from young animals. The addition of TCGF to cultures containing responding cells alone that had not been pretreated with anti-I-A plus complement resulted in high levels of background proliferation. This is indicative of a high number of preexisting I-A-positive, activated, TCGF-responsive T cells in these mice. These activated cells could also be removed by treatment with anti-I-A antibody and panning on anti-mouse Ig plates, or by BUdR and light killing of those cells proliferating in the presence of TCGF or purified IL-2. Prior treatment of the responding cells with anti-Lyt 2 and complement did not effect the AMLR. An NZB AMLR responding cell line was established using these methods. This line retained haplotype specificity in a proliferation assay. Limiting dilution analysis of the precursor frequency of AMLR responding cells in the nonautoimmune C58 and BALB/C strains in culture medium with TCGF gave a frequency of between 1 in 35,000 and 1 in 88,000. In young, AMLR-positive, NZB mice, supplementation with TCGF yielded precursor frequencies within the normal range. In older NZB mice, the addition of TCGF resulted in increased background proliferation of preactivated, IA⁺ T cells. After removal of these cells with anti-I-A plus complement, AMLR responding cells were found at normal frequency levels when stimulated in the presence of TCGF. In the oldest animals tested (greater than 18–20 weeks), normal precursor frequencies could not be demonstrated even after this treatment, representing a true decline in the AMLR responding cell number. AMLR deficiency in NZB mice appears therefore to be the result of the combined effects of decreased lymphokine production, excessive T-cell activation, and finally decreased numbers of AMLR responding cells.