Studies on the ovine mast cell : heterogeneity and involvement in cutaneous inflammation

• Main Author: Sture, Gordon Hunter
• Published: University of Edinburgh 1996
• Subjects: 571.1
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.662576

The distribution of the granule chymase Sheep Mast Cell Proteinase (SMCP) was determined in trachea, bronchus, bronchial lymph node, thymus, spleen, liver, flank skin, abomasum, duodenum, jejunum, ileum, colon and mesenteric lymph node by immunohistochemistry and by ELISA using a polyclonal, affinity purified anti-SMCP antibody. The toluidine blue and SMCP-positive cell counts were closely correlated for all tissues examined (r<SUP>2</SUP> = 0.96, P<0.001), with the exception of skin and liver. On the basis of reactivity to the anti-SMCP antibody, two populations of ovine mast cells were identified. SMCP-positive cells (analogous to the gastronintenstinal or mucosal mast cell [MMC] subset) were present in all tissues examined whereas SMCP-negative cells were present in skin (the putative ovine connective tissue mast cell [CTMC] subset) and comprised-98% of the ovine dermal mast cell population. The functional heterogeneity of the ovine dermal mast cell population was investigated in cutaneous challenge studies using the secretagogues calcium ionophore A23187 (A23187), substance P (sP) and compound 48/80 (48/80), which are known to activate CTMC subsets in other species. Although only A23187 and sP evoked an immediate weal response (P<0.05; Mann-Whitney U test [MW]), all three agents evoked dermal neutrophil influx (P<0.05; MW) with extensive mast cell degranulation (P<0.05; MW), thus identifying these agents as putative ovine dermal mast cell secretagogues. As SMCP may be released into the dermis following degranulation, its effect in ovine skin <I>in vivo</I> was investigated. SMCP (36μg - 36ng/50μl) evoked a dose-dependent immediate cutaneous response characterised by weal formation (maximal by three hours after injection (P<0.05; MW)) accompanied by dermal neutrophil influx (P<0.05; MW) and concomitant mast cell degranulation (P<0.05; MW). There was no subsequent delayed component to this response (24 to 72 hours).