The mRNA expressions of PD-1 , PD-L1 , and meq in MD-derived tumor cells. (A) The expression of meq mRNA was confirmed in serial sections of spleen and tumor samples from experimentally infected chickens by in situ hybridization. Samples were collected at 35 d.p.i. Positive signals were detected mononuclear cells infiltrating into the renal tubulointerstitium (upper panel) and in white pulp of spleen (lower panel). (B) Mononuclear cells infiltrating into the renal tubulointerstitium and adjacent renal cells, and white pulp of the spleens from infected or uninfected chickens were captured by LMD. Panels show the targeted areas before (left) and after (right) capture. (C) The expression of PD-1, PD-L1, and meq mRNA was confirmed by RT-PCR using RNA isolated from LMD-captured samples.