Viral transcription in the two examples of tissue, GALT and spleen, at 14, 21 and 28 days pi. In situ hybridization was performed with radiolabeled SIV-specific RNA and SIV RNA-positive cells appear black. Montage of large image (magnification ×10) of single section, among 4 or 2 sections examined from GALT and spleen, respectively. The encircled regions in the spleen were the most numerous for productive cells. The headed arrow points to a few SIV RNA positive cells founded at day 21 and 28 in the GALT.