CD4 and vasculitis: An early light and electron microscopical study identified the vasculitis in MCF to be mediated by lymphocytes/lymphoblasts and fewer monocytes/macrophages.40 A subsequent study on 2 bovine MCF cases stated that macrophages made up more than half of the cells in the leukocyte infiltrates, accompanied by equal numbers or less T-cells (CD8+, CD4+).49 A few years later, the investigation of a calf and a bison with MCF found T-cells (CD3+; predominantly CD8+, no CD4+ cells) to dominate the infiltrates, accompanied by low numbers of monocytes/macrophages.68