has part has plasma membrane part develops from capable of monoblast promonocyte A precursor in the monocytic series, being a cell intermediate in development between the monoblast and monocyte. This cell is CD11b-positive and has fine azurophil granules. BTO:0004657 Promonocytes are precursor cells in the mononuclear phagocyte system, which includes the progenitors in the bone marrow, circulating monocytes and macrophages in various tissues. During monocytopoiesis, promonocytes form after monoblasts differentiate, and precede the development of monocytes and macrophages, which play an integral role in the immune system. Promonocytes are large, often round cells with a high nucleus to cytoplasm ratio. Their cytoplasm is laden with small azurophilic granules, and they are similar in appearance to myelocytes and metamyelocytes. The maturation into monocytes is the key function of promonocytes. Once matured, they navigate their way to the bloodstream and their primary role comes into effect. Monocytes circulate in the blood for a few days before migrating to tissues to become either macrophages or dendritic cells. These cells then proceed to ingest pathogens like bacteria and viruses, helping to keep the body healthy. Thus, promonocytes play a central role in the immune system by paving the way for the development of cells that fight off toxins and attacks. Beyond their immune response role through differentiation, promonocytes may participate in processes such as wound healing and inflammation regulation. Defects or disruptions in promonocyte function have been linked to health disorders, including monocytic-lineage leukemias such as chronic myelomonocytic leukemia (CMML), although it is worth noting that morphologic distinction between promonocytes and other monocytic cells of various differentiation levels is difficult. (This extended description was generated by ChatGPT and reviewed by the CellGuide team, who added references, and by the CL editors, who approved it for inclusion in CL. It may contain information that applies only to some subtypes and species, and so should not be considered definitional.) Morphology: Mononuclear cell, diameter 14-18 _M, fine azurophilic granules; markers: CD11b (shared with many other myeloid cells); location: Adult: bone marrow; Fetal: Liver, Yolk Sac; role or process: hematopoiesis, monocyte development; lineage: hematopoietic, myeloid. https://cellxgene.cziscience.com/cellguide/CL_0000559 ZFA:0009253 FMA:83551 myeloid cell monopoietic cell monocyte differentiation azurophil granule integrin alpha-M