Young rete ridge keratinocytes are preferred targets in cutaneous graft-versus-host disease

Recent data show that stem cells in primate epidermis are concentrated at the bases of rete ridges. Because the early lesions of graft-versus-host disease (GVHD) in the vertebrate skin are in basal epidermis and hair follicle cells, the authors hypothesized that stem cells or their early progeny might be targeted. In this study they used morphometric methods to examine the distribution of the lesions of GVHD in the skin and lip of human bone marrow allograft recipients. They found that rete ridges are the primary sites of attack in early GVHD of the skin. They also found that the concentration of stem cells in ridges for various anatomic sites (body or arm, palm or sole, and lip) is directly proportional to the frequency and concentration of the lesions of GVHD. Osmotic fragility and the expression of early differentiation antigens related to the major histocompatibility complex are discussed as potential explanations for this phenomenon.