Detection of mouse IL-8 receptor homologue expression on peripheral blood leukocytes and mature myeloid lineage cells in bone marrow

Interleukin-8 (IL-8) exhibits activities on bone marrow progenitor cells such as regulation of their growth and their mobilization into peripheral blood. In order to clarify the molecular mechanism of the effects of IL-8 on mouse bone marrow cells, we examined the cellular distribution of mouse IL-8 receptor homologue by an immunofluorescence analysis. Peripheral blood Gr-1⁺ mature granulocytes, and a substantial portion of NIK1.1⁺ natural killer cells in peripheral blood and spleen were stained positively with anti-mouse IL-8 receptor homologue antibody, whereas CD4⁺, CD8⁺, or B220⁺ lymphocytes in peripheral blood and spleen, and thymocytes were not. Moreover, a small portion of ER-MP20⁺ monocytes in peripheral blood but neither peritoneal resident nor bone marrow macrophages were stained with anti-IL-8 receptor homologue antibody. In bone marrow, mature granulocytes and to a lesser degree, metamyelocytes and myelocytes expressed IL-8 receptor homologue. Moreover, lineage marker (Lin)^-c-kit⁺ bone marrow progenitor cells started to express IL-8 receptor homologue only 5 days after in vitro culture with IL-3 and stem cell factor when metamyelocytes and myelocytes appeared. These results indicated that myeloid lineage cells express a substantial number of IL-8 receptor homologues only at the stage of myelocytes.