STRUCTURAL FEATURES INVOLVED IN THE MITOGENIC ACTIVITY OF BORDETELLA-PERTUSSIS LIPOPOLYSACCHARIDES FOR SPLEEN-CELLS OF C3H HEJ MICE/

Spleen cells from the C3H/HeJ mouse strain cannot be stimulated by man y smooth-type lipopolysaccharides (LPSs), and by the main biologically -active region (lipid A) of these molecules. The genetic origin of thi s defect (expression of the mutant allele Lps(d) at the chromosome 4 l ocus) was established over 20 years ago, but its biochemical nature ha s remained undefined. Several investigators have noted, however, that some particular LPSs can bypass this defect, and stimulate the prolife ration of C3H/HeJ B lymphocytes. In this study we compare the mitogeni c activities of the LPSs isolated from a wild strain (1414) and from a mutant 'rough' strain (A100) of Bordetella pertussis. Both LPS-1414 a nd LPS-A100 were mitogenic for C3H/HeJ spleen cells, but their lipid A fragments were not. This indicates that a carbohydrate structure prox imal to lipid A is involved in the mitogenic activity. However, the is olated polysaccharides were not mitogenic. Four sugars are common to b oth LPS-1414 and LPS-A100: an heptose, and three sugars bearing free a mino groups. After removal of these four sugars from the LPSs by nitro us acid treatment, the recovered lipooligosaccharides were not mitogen ic in Lps(d) spleen cells. The results suggest that substructures pres ent in lipid A and in this group of four sugars are both required for induction of a mitogenic effect in Lps(d) splenocytes, whereas lipid A alone can stimulate Lps(n) spleen cells.