CLDN1 and Alzheimer disease: To determine whether AD-related alterations in the expression of keratinocyte differentiation markers can be obtained in vitro, sections of the RHEs were immunostained with anti-filaggrin (Figure 1b,f,j,n,r), anti-loricrin (Figure 1c,g,k,o,s) and anti-claudin-1 (Figure 1d,h,l,p,t) antibodies.