aging research is still currently evolving. Recent studies have shown that haematopoietic progenitor cells contribute to immune responses in the body. They have been shown to respond a range of inflammatory cytokines. They also contribute to fighting infections by providing a renewal of the depleted resources caused by the stress of an infection on the immune system. Inflammatory cytokines and other factors released during infections will activate haematopoietic progenitor cells to differentiate to replenish the lost resources. Examples The characterization or the defining principle of progenitor cells, in order to separate them from others, is based on the different cell markers rather than their morphological appearance. Satellite cells found in muscles. They play a major role in muscle cell differentiation and injury recoveries. Intermediate progenitor cells formed in the subventricular zone. Some of these transit amplifying neural progenitors migrate via rostral migratory stream to the olfactory bulb and differentiate further into specific types of neural cells. Radial glial cells found in developing regions of the brain, most notably the cortex. These progenitor cells are easily identified by their long radial process. Bone marrow stromal cells found in the epidermis and make up 10% of progenitor cells. They are often classed as stem cells due to their high plasticity and potential for unlimited capacity for self-renewal. Periosteum contains progenitor cells that develop into osteoblasts and chondroblasts. Pancreatic progenitor cells are among the most studied progenitors. They are used in research to develop a cure against diabetes type-1. Angioblasts or endothelial progenitor cells (EPC). These are very important for research on fracture and wounds healing. Blast cells are involved in generation of B- and T-lymphocytes, which participate in immune responses. Boundary cap cells from the neural crest form a barrier between the cells of the central nervous system and cells of the peripheral nervous system. Boundary cap neural crest stem cells promote survival of mutant SOD1 motor neurons. Development of the human cerebral cortices Before embryonic day 40 (E40), progenitor cells generate other progenitor cells; after that period, progenitor cells produce only dissimilar mesenchymal stem cell daughters. The cells from a single progenitor cell form a proliferative unit that creates one cortical column; these columns contain a variety of neurons with different shapes. See also Induced progenitor stem cells Endothelial progenitor cell References Stem cells Biotechnology Cell biology Developmental biology Cloning