The aim of this study was to characterize infiltrating immune cells in cervical stroma biopsy samples from patients diagnosed with cervical intraepithelial neoplasias (CINs) who were treated with IFN- α 2b. The authors studied 13 volunteers who were diagnosed with Cervical intraepithelial neoplasiaCIN II or III and who received intra-lesional treatment with IFN-α 2b. They collected pre- and post- treatment biopsies from each patient. They also examined the slides under a common optical microscope with a X400 lens for biopsy sample sections that were labeled with immunohistochemistry for T lymphocyte, B lymphocyte, natural killer cell, macrophage, iNOS, and perforin markers. The presence of immune response cells in the lesion was observed after treatment with intralesional IFN-α 2b in patients with CIN II/III changes, a reduction in CD4+ and CD8+ T lymphocyte infiltration in the women who responded well to treatment. However, there was a significant increase in these markers in samples from women who did not respond to treatment. Nonetheless, immunotherapy with IFN-α 2b administered intralesionally in patients with CIN II/III yields favorable results in patients who do not smoke.