Tissue identification of B henselae in suppurative lymphadenitis. (A-B, D) Immunohistochemistry of lymph node sections from a CSD case using anti-BH illustrates the location of B henselae bacilli. Reactivity is particularly obvious within the necrotic area (* in A) where positive bacilli are found as small clusters or single elements as illustrated by the high-power field in panel B. Double staining using CD20, CD68, and anti-BH shows B henselae bacilli intermingled with CD20⁺ B cells (D) and CD68⁺ macrophages (E). (C) Expression of B henselae DNA was determined by PCR amplification using specific primers. Lane – indicates no template; lanes 1-2, CSD cases; lanes 3-5, mycobacterial lymphadenitis cases; lane 6, positive control (B henselae–infected DCs); lane 7, molecular weight ladder. Immunoperoxidase technique for anti-BH counterstained with Meyer hematoxylin (A-B). Combined immunoperoxidase and immunofluorescence for anti-BH and CD20 or CD68 (D-E; see “Tissues and staining procedures” for details). Original magnification, × 200 (A,D,E) and × 600 (B).