Lymphocytocidal lymphocyte trapping: Organ and species occurrence and increase in the presence of tumor metastasis

The frequency of lymphocytocidal trapping cells (LTC) in different organs and species, and factors influencing the frequency of LTC have been investigated. Lymphocytocidal trapping cells were found in cultures of human lymph nodes from 5 anatomic locations and in cultures of human tonsils, spleen, and thymus. LTC were present in 4.5% of 2,034 cultures of human lymph nodes and tonsils. When 19 lymph node cultures were challenged with allogeneic lymphocytes the frequency rose to 45% or more (P < 0.005). In contrast, LTC were not found in 274 cultures of 50 explanted lymphoid tissues from 4 nonprimate species, namely, chicken, cow, dog and rat (P < 4 x 10^-6), and they were not found in 7 rat cultures challenged with syngeneic lymphocytes (P = 0.05). Because LTC were found in cultures of a monkey lymph node as well as the human tissues, there is the implication that trapping may be restricted to primate species. Possibly, the culture method used is selective for primate LTC. There was a higher than expected frequency of multiple LTC in individual cultures, consistent with a nonrandom distribution of LTC in lymph node tissue. LTC were 2.3 times as frequent in cultures of cancer-free lymph nodes from patients with metastases as in those from patients with cancer that had not metastasized (P = 0.026). All of the findings from this study and of an accompanying report are consistent with the hypothesis that the LTC is a distinct cell type with lymphocytocidal properties and contributes to the control of human lymphocyte populations.