Characterization of surface markers of bovine gut mucosal leukocytes using monoclonal antibodies

Abstract

The surface phenotypes of bovine intestinal leukocytes isolated from the intraepithelium (IEL), lamina propria (LPL) and Peyer's patches (PPL) of the small intestinal mucosa of normal adult cows were determined using monoclonal antibodies (mAb) specific to adult bovine peripheral blood leukocytes (PBL). Laser flow cytometric (LFC) analysis demonstrated that IEL contained significantly ( P<0.1 to 0.02) fewer cells (26%) expressing the panT cell phenotype in comparison to LPL (38%) and PPL (44%). Similarly, significantly ( P<0.01 to 0.001) lower numbers of B cells were observed among IEL (10%) compared to LPL (28%) and PPL (33%). While approximately equal numbers of B7A1 + “null” cells (10%) and DH59B + “Ia + monocytes/granulocytes” (16.5%) were observed among the three intestinal cell populations, IEL contained significantly ( P<0.1 to 0.05) lower numbers (19%) of T helper (Th) cells in comparison to LPL (44%) and PPL (38%). In contrast, lymphocytes with the T cytotoxic/suppressor (Tc/s) phenotype were significantly lower ( P<0.01 to 0.001) among LPL (14.5%) compared to IEL (25%) and PPL (23%). While the numbers of cells expressing class I major histocompatibility complex (MHC) surface antigens (H58A +) were approximately equal among LPL (79%) and PPL (87%), a significant difference ( P<0.02) was observed between IEL (71%) and PPL. Similarly, while approximately equal numbers of cells expressing the MHC class II surface phenotype were observed among LPL (42%) and PPL (46%), IEL contained significantly ( P<0.1) fewer (31%) MHC class II cells in comparison to PPL. Enrichment for T cells by plastic adherence and Sephadex G-10/nylon wool fractionation revealed a significant ( P<0.01) and proportional increase in T lymphocyte subsets expressing panT, Th and Tc/s phenotypes among the three cell populations. Similarly, enrichment for B cells by the same techniques showed a significant ( P<0.01) and proportional increase in cells expressing the panB cell phenotype among LPL and PPL. Marked differences in cell size distribution and cell surface density were observed when the three intestinal leukocyte populations were compared by LFC using monoclonal antibodies directed at various cell surface markers. Furthermore, considerable quantitative variations of each cell surface marker were observed among the individual animals tested. The results of this study indicate that bovine IEL, which contain a high percentage of cells (>30%) with no known phenotype are significantly different from LPL and PPL which are phenotypically similar cell populations. Furthermore, the recently developed mAb can be used to phenotype leukocytes from tissues other than blood and, particularly in the case of IEL, these phenotypes differ considerably from those found in peripheral blood.