The lack of expression of mature keratins by the expanding CD34+ hair follicle-associated keratinocytes, particularly Krt 14 which is highly expressed by keratinocytes throughout the basal layer of the epidermis, further highlights the distinction between the cells that expand in response to infection and the more differentiated keratinocyte sub-types forming the basal and supra-basal epidermal layers (Blanpain and Fuchs, 2009; Hsu et al., 2011; Hsu and Fuchs, 2012). This evidence concerns the gene CD34 and infection.