CD56^bright NK cells are present in human lymph nodes.

(A) CD56⁺ and CD94⁺ lymphocytes are present in the paracortical T-cell areas of normal human lymph nodes. Low-power (× 40, left) and high-power (× 100, right) photomicrographs of normal human lymph nodes stained for CD56 (top panels) and CD94 (bottom panels). Results are representative of 2 reactive lymph nodes. (B) CD56⁺CD3⁻ lymphocytes were observed in the parafollicular T-cell areas of human lymph nodes. Low-power (× 40, left) and high-power (× 100, right) photomicrographs of normal human lymph nodes evaluated for CD56 expression using in situ RT-PCR (top panels). High-power photomicrographs of similar sections from lymph nodes colabeled with anti-CD3 mAb and CD56 via in situ PCR demonstrating that the CD56⁺ cells lack CD3 expression (bottom panels). Results are representative of at least 4 different experiments. (C) Distinct populations of CD56^brightCD3⁻ NK cells were observed via flow cytometry in normal human lymph nodes. Flow cytometric density plots are shown gated on lymphocytes stained with mAbs reactive to CD56 and CD3 (left), CD56 and CD16 (middle), and CD56 and CD94 (right). Percentage of lymphocytes in each boxed region is shown. Results are representative of 3 independent experiments on at least 3 normal human lymph nodes.