PMC

Diagrammatic representation of the human skin explant assay. GVHR, graft versus host reaction; HLA, human major histocompatibility complex; MLC, mixed lymphocyte culture.

Correlation between keratinocyte apoptosis and histopathological gradings of graft versus host disease in the skin explant model. As the severity of the graft versus host reaction (GVHR) increases, there is a corresponding increase in the degree of apoptosis observed (mean values are indicated by the bar). An unpaired t test comparing mean values of apoptosis between grade 0–I (regarded as background) and grade II–IV, at a 95% confidence interval, gave a p value of ≤ 0.0001.

(A) Haematoxylin and eosin stained skin section from the skin explant assay showing a grade 0–I reaction. This is normal skin and considered as background. Mild vacuolisation of basal cells is seen, together with the occasional dyskeratotic body. (B) Haematoxylin and eosin stained skin section from the skin explant assay showing a grade III reaction. This is considered a positive result and a severe graft versus host reaction. (I) Diffuse vacuolisation of basal cells, with (ii) scattered dyskeratotic bodies, and (iii) subepidermal cleft formation. (C) Grade I terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL) biopsy showing < 1% apoptotic cells (brown nuclei). Most of this skin section shows negative staining (blue counterstain). (D) Grade III TUNEL biopsy, showing 5.3% apoptotic cells (arrows).