Interleukin-2 production in response to phytohemagglutinin is not necessarily dependent upon the T3-mediated pathway of T-cell activation

Neuroendocrine Differentiation of Lung Cancer Cells Impairs the Activation of Antitumor Cytotoxic Responses in Mice

Lung cancer has the highest mortality among all types of cancer; during its development, cells can acquire neural and endocrine properties that affect tumor progression by releasing several factors, some acting as immunomodulators. Neuroendocrine phenotype correlates with invasiveness, metastasis, and low survival rates. This work evaluated the effect of neuroendocrine differentiation of adenocarcinoma on the mouse immune system. A549 cells were treated with FSK (forskolin) and IBMX (3-Isobutyl-1-methylxanthine) for 96 h to induce neuroendocrine differentiation (NED). Systemic effects were assessed by determining changes in circulating cytokines and immune cells of BALB/c mice immunized with PBS, undifferentiated A549 cells, or neuroendocrine A549_NED cells. A549 cells increased circulating monocytes, while CD4⁺CD8^- and CD4⁺CD8⁺ T cells increased in mice immunized with neuroendocrine cells. IL-2 and IL-10 increased in mice that received untreated A549 cells, suggesting that the immune system mounts a regulated response against adenocarcinoma, which did not occur with A549_NED cells. Cocultures demonstrated the cytotoxic capacity of PBMCs when confronted with A549 cells, while in the presence of neuroendocrine cells they not only were unable to show cytolytic activity, but also lost viability. Neuroendocrine differentiation seems to mount less of an immune response when injected in mice, which may contribute to the poor prognosis of cancer patients affected by this pathology.

Proliferative responses of human intraepithelial lymphocytes to various T-cell stimuli

Human intraepithelial lymphocytes (IEL) are CD8+ T cells located between intestinal epithelial cells, capable of only minimal proliferation to mitogens but brisk proliferation to mitogens combined with sheep red blood cells. This study examines this differential response of IEL. Both IEL and CD8+ T lymphocytes from the peripheral blood are predominantly CD2+, CD3+, CD4-, CD5+, CD8+, and express the alpha beta subunits of the T-cell receptor. Human IEL express the same densities of the CD2, CD3, and CD8 antigens but a lower density of the CD5 antigen than do peripheral blood CD8+ T cells. The proliferation of IEL is significantly less than that of peripheral blood CD8+ T lymphocytes in response to phytohemagglutinin, to concanavalin A, or to anti-CD3 antibody bound to Sepharose (p less than 0.05). Supplementing IEL with interleukin-1, interleukin-2, or autologous peripheral blood macrophages does not completely reconstitute the proliferative response of IEL to these stimuli. Rather, the low proliferation of IEL to these stimuli is due to incomplete activation, as demonstrated by the low percentage of CD25 (Tac)+ lymphocytes with concanavalin A or the low density of the CD25 antigen with phytohemagglutinin. Both IEL and peripheral blood CD8+ T lymphocytes proliferate minimally in response to alloantigens or to interleukin-2, but briskly in response to stimuli of the CD2 receptor such as the combination of anti-T11(2) and anti-T11(3) antibodies or mitogen and sheep red blood cells. The sheep red blood cells enhance the mitogen-induced response of IEL by augmenting events of activation, both interleukin-2 production and interleukin-2 receptor expression. Thus, IEL represent an unusual compartment of CD2+, CD3+ T lymphocytes that are activated more completely by stimuli of the CD2 receptor than by stimuli of the CD3 receptor or by T-cell mitogens.