MODIFICATIONS IN TISSUE HISTAMINE LEVELS IN MAST CELL-DEFICIENT MICE (W W-V) AND IN THEIR LITTERMATES (W-V/+, W/+ AND +/+) GRAFTED WITH A METHYLCHOLANTHRENE-INDUCED FIBROSARCOMA - CORRELATION WITH TUMOR REJECTION/

There is evidence that mast cells and their degranulation products are involved in resistance against tumours. Previously, we have shown tha t tumour incidence and growth were inversely correlated with basal his tamine levels, i.e. mast cell numbers, in tissues of W/W-v (mast cell- deficient), W-v/+ (partially mast cell-depleted), and +/+ (mast cell-s ufficient) mice, and that histamine levels were increased in numerous tissues of tumour-bearing animals, including C57BL/6 and C3H mice, Spr ague-Dawley and Commentry rats. The aim of this work was to analyse th e incidence and growth of a grafted tumour (fibrosarcoma MC-B6-1) in W /+ mice, as compared with W/W-v, W-v/+ and +/+ mice, and to study the modifications in tissue histamine levels in W/+, W/W-v, W-v/+ and +/tumour-grafted mice, in order to determine whether or not these modifi cations were correlated with resistance to tumours. We report confirma tion that tumour incidence and growth are inversely correlated with ba sal tissue histamine levels in W/W-v, W-v/+, and +/+ fibrosarcoma-bear ing mice. However, in W/+ mice (normal tissue histamine levels), tumou r incidence was the same as in W-v/+ mice. Histamine levels in tissues of W/W-v, W-v/+, W/+ and +/+ tumour bearing mice were not significant ly different from those in controls. They were higher in some tissues of W-v/+ mice rejecting the tumour than in W-v/+ mice not rejecting th e tumour. However, in W/+ and +/+ mice, histamine levels were not sign ificantly different, and even tended to be lower in most tissues of mi ce rejecting the tumour than in mice accepting the tumour. Overall, th ese results suggest that resistance to tumours cannot be ascribed sole ly to mast cells, and that other mechanisms may also be involved. Thus , further experiments are needed to clarify the exact role of mast cel ls and mast cell-derived mediators and cytokines in the defence agains t tumours.