Human Melanocytes and Keratinocytes Exposed to UVB or UVA In Vivo Show Comparable Levels of Thymine Dimers  Antony R. Young  Journal of Investigative Dermatology  Volume 111, Issue 6, Pages 936-940 (December 1998) DOI: 10.1046/j.1523-1747.1998.00435.x Copyright © 1998 The Society for Investigative Dermatology, Inc Terms and Conditions

Figure 1 Thymine dimers within melanocyte nuclei can be identified by triple fluorescence staining. (a) A double exposure image in which nuclei are identified by exciting DAPI with 330 nm to give blue fluorescence (λmax = 461 nm) and melanocytes are recognized by exciting FITC, conjugated with the B8G3 antibody, to give a green fluorescence (λmax = 525 nm). The machine software is able to store the location of nuclei and melanocytes. (b) Thymine dimers identified by CY3 conjugation with TDM1 within the nuclear area defined with DAPI and specifically within the melanocytes identified by FITC. Under the double exposure conditions of (b), CY3 excited at 577 nm is red (λmax = 605 nm) in keratinocyte nuclei but orange-red in melanocytes, the cytoplasm of which appears yellow-green after FITC excitation at 485 nm. Thymine dimers within basal cell keratinocytes are recognized by their location (b).Scale bar: 20 μm. Journal of Investigative Dermatology 1998 111, 936-940DOI: (10.1046/j.1523-1747.1998.00435.x) Copyright © 1998 The Society for Investigative Dermatology, Inc Terms and Conditions

Figure 2 Dose–response curves for thymine dimers in melanocytes and basal keratinocytes are similar at UVB and UVA wavelengths studied. Linear regression analysis of representative melanocyte and basal keratinocyte data for one volunteer for each wavelength show no differences in dose–response curves of each cell type at (a) 300 nm, (b) 320 nm, (c) 340 nm, and (d) 360 nm. These regression data, which have not been forced through the zero point, show a highly significant (p ≤ 0.01) linear relationship between MED and TT levels that are indicated by MF less background readings. Regression parameters for all volunteers are given inTable 2. Note that the data inFigure 2 relate to volunteer 1 at each wavelength and that the zero points for the two cell types overlap. Journal of Investigative Dermatology 1998 111, 936-940DOI: (10.1046/j.1523-1747.1998.00435.x) Copyright © 1998 The Society for Investigative Dermatology, Inc Terms and Conditions