Functional nuclei of LPS-nonresponder C3H/HeJ mice after transfer into LPS-responder C3H/HeN cells by cell fusion

Abstract

Splenic lymphocytes of C3H/HeJ mice are defective in responding to the mitogenic activity of bacterial lipopolysaccharide (LPS)^1–4, which has been attributed to a mutation at a single gene locus on chromosome 4 (ref. 5). It was suggested that C3H/HeJ mice lack a cell-surface receptor necessary for LPS recognition^6,7. However, specific binding of ¹²⁵I-labelled lipid-A of LPS to B cells was found to be equivalent in LPS-responder and LPS-nonresponder C3H/HeJ, C57BL/10 ScCR and C57BL/10 ScN mice⁸. This suggests that the genetic defect in C3H/HeJ mice is related to triggering mechanisms rather than to LPS binding. We recently established a method for separating mouse splenic lymphocytes into karyoplasts (minicells) and cytoplasts (enucleated cells) with high purity⁹. This method makes possible the exchange of nuclei from one type of lymphocyte to another. In the present study, karyoplasts were purified from LPS-nonresponder C3H/HeJ mice and transferred to mitomycin C-treated or X ray-irradiated splenic lymphocytes taken from LPS-responder C3H/HeN mice by fusion with polyethyleneglycol. These reconstituted hybrid cells could respond to LPS, suggesting that nuclei from C3H/HeJ mice could be activated by LPS if proper signals were provided from cell-surface receptors. Moreover, responsiveness to concanavalin A (Con A) of mitomycin C-treated or X ray-irradiated lymphocytes was also recovered by the microinjection of karyoplasts from untreated lymphocytes.