Activation and signaling status of human lamina propria T lymphocytes

In this study, proliferative responses of human lamina propria T lymphocytes were examined in vitro. The response of lamina propria T lymphocytes to Sepharose-bound anti-CD3 antibody plus interleukin 2 was significantly lower than the response of autologous peripheral blood T lymphocytes, whereas the responses of lamina propria T lymphocytes to anti-T11(2/3) antibodies plus sheep erythrocytes or anti-CD28 antibody plus interleukin 2 were largely preserved. After coculture with mucosa supernatant, peripheral blood T lymphocytes showed a similar pattern of reactivity as lamina propria T lymphocytes. This reduced reactivity to T-cell antigen receptor stimulation appears to exist at the level of signal transduction, because triggering of CD3 induces low amounts of intracellular inositol 1,4,5-triphosphate and no free calcium increase in lamina propria T lymphocytes when compared with peripheral blood T lymphocytes. This study indicates that the antigen receptor-dependent activation pathway of lamina propria T lymphocytes for proliferation is down-regulated by intestinal mucosa derived factor(s) and that the alternative pathways mediated by CD2 or CD28 are largely preserved. Based on previous data that lamina propria T lymphocytes can provide help to B cells, it is possible that these alternative activation pathways play an important role in T-B cell interaction in the gut.

Down-regulation of protein kinase C activation in human lamina propria T lymphocytes: influence of intestinal mucosa on T cell reactivity

Human lamina propria T lymphocytes (LPL-T) were shown to have lower proliferative responses to CD3 triggering than autologous peripheral blood T lymphocytes (PBL-T), yet preserved their responsiveness to CD2 stimulation. In order to elucidate the basis of these differences, freshly recovered human LPL-T and autologous PBL-T were stimulated with CD2 monoclonal antibodies anti-T11(2/3) plus sheep red blood cells and phorbol 12,13-dibutyrate (PBu2) plus ionomycin, respectively. LPL-T showed invariably lower responses to PBu2 plus ionomycin than PBL-T. In contrast, LPL-T still preserved proliferation to CD2 activation even when their responses to PBu2 plus ionomycin were decreased almost to background levels. Preincubation of PBL-T with intestinal mucosa supernatant led to a similar reactivity as observed in fresh LPL-T. Moreover, the protein kinase C (PKC) inhibitor sphinganine was able to inhibit DNA synthesis to stimulation with PBu2 plus ionomycin but not to CD2 triggering. This study suggests that CD2-induced proliferation is not dependent on PKC activation and that down-regulation of PKC activation may be one of the mechanisms for inhibition of the CD3-Ti-dependent activation pathway in LPL-T by intestinal mucosa-derived influences in vivo.

Stimulation of FACS-analysed CD4+ and CD8+ human tumour-infiltrating lymphocytes with ionomycin + phorbol-12,13-dibutyrate does not overcome their proliferative deficit

Human tumour-infiltrating lymphocytes (TIL) were prepared by enzyme digestion from a series of different tumours and were purified on a fluorescence-activated cell sorter (FACS II) according to their CD4+ and CD8+ phenotype. CD4+ and CD8+ TIL were stimulated separately in a low density microculture system with phytohaemagglutinin (PHA) or with ionomycin plus phorbol-12, 13-dibutyrate (PDBu). The PHA-induced proliferation of TIL was highly decreased when compared with control peripheral blood lymphocytes. A decreased proliferation of TIL was also observed when cells were stimulated with ionomycin plus PDBu, a combination which is thought to circumvent early events associated with lymphocyte activation. Some TIL were also plated in limiting dilution where they showed decreased frequencies of proliferating T cell precursors. The data suggest that one component of the inhibition of TIL must be acting 'downstream' of the early events of lymphocyte activation.

Preferential clonogenic deficit of CD8-positive T-lymphocytes infiltrating human solid tumors

The vast majority of tumor infiltrating lymphocytes (TIL) are either CD4+ or CD8+ T-lymphocytes. In order to examine directly the functional capabilities of the individual CD4+ and CD8+ TIL subsets we performed cell sorting of double immunofluorescence-labeled TIL recovered from 15 biopsies by enzyme digestion. These CD4+ and CD8+ TIL subsets were compared with similar subsets of T-lymphocytes from peripheral blood of normal subjects. Both CD4+ and CD8+ TIL showed a reduced clonogenicity as assessed quantitatively by limiting dilution analysis in a microculture system which allows every normal T-lymphocyte to undergo clonal expansion. The reduced clonogenic potential was unequally distributed among the CD4+ and CD8+ subsets with the CD8+ TIL showing a significant reduction of the frequency of proliferating T-lymphocyte precursors compared to the CD4+ TIL (with a median of 1/50 proliferating T-lymphocytes in CD8+ TIL versus a median of 1/11 in CD4+ TIL). The reduced response of CD8+ TIL was not caused by suppressor cells, lack of surface expression of CD2 and CD3 antigens nor of the alpha, beta T-cell receptor, nor by an accumulation of CD8+ cells of large granular lymphocyte morphology. Using low density cultures, the highly purified CD4+ and CD8+ TIL were stimulated either via the T-cell receptor or the CD2-mediated antigen-independent pathway of activation. Whereas CD8+ TIL did not respond to either stimulus the CD4+ TIL showed evidence of responder and nonresponder groups. In addition, we show that the deficient response obtained by triggering CD4+ TIL via the TCR can be restored by activation of the antigen-independent pathway. Finally, a total of 94 clones from four different TIL samples were obtained by limiting dilution and examined for their respective helper and cytolytic capabilities: 57% of the CD4+ TIL clones were able to produce interleukin 2 and 93% of the CD8+ TIL clones demonstrated cytolytic activity mediated by the T-cell receptor complex, indicating that the functional potential of proliferating TIL is intact.

Proliferative and cytolytic potentials of purified human tumor-infiltrating T lymphocytes. Impaired response to mitogen-driven stimulation despite T-cell receptor expression

Using limiting dilution analysis (LDA) we have previously shown that in most instances, the frequency (F) of proliferative T lymphocyte precursors (PTL-P) was strikingly reduced in tumor-infiltrating lymphocytes (TIL). In this study involving 19 cases, we show that the impaired clonogenic potential of CD2+ TILs is primarily caused by an intrinsic defect rather than to suppressor T cells or to a direct effect of the tumor cells usually present in the culture system. This was demonstrated by experiments in which the F of PTL-Ps was quantitated both in highly purified CD2+ TILs (using a cell-sorter) and in non-purified TIL suspensions (still containing tumor cells), which originated from the same biopsy specimen. The F of PTL-Ps was virtually identical in either sorted or nonsorted suspensions and the data from LDA were always consistent with the single-hit Poisson model, indicating that no suppressor cells interfered with growth of CD2+ TIL. Stimulation of sorted CD2+ TIL in low-density cultures by either phytohemagglutinin or anti-CD3-monoclonal antibody (MAb) indicated that the antigen-dependent activation pathway was impaired, although structurally intact T-cell receptor (TCR) complexes were apparently expressed, as assessed by immunofluorescence. The depressed proliferative response of CD2+ TIL could not be reversed in vitro when phorbol-esters were used in combination with ionomycin, which bypass the TCR. Nevertheless, 180 clones obtained from 8 cases were analyzed for their cytolytic activity. The majority mediated specific lytic activity (against unknown antigens), as assessed by lectin-dependent cell cytotoxicity, whereas only 6% of them manifested lymphokine-activated killing on appropriate targets.

Epidemiologic survey of vibration syndrome among riveters, chippers and grinders in the railroad system of the People's Republic of China

Vibration syndrome caused by hand-held vibrating tools in 14 locomotive and rolling stock plants in four regions of the People's Republic of China (south, north, middlewest, and northeast) and the influence of climatic factors on its prevalence rate were studied. For 1,028 male workers (705 riveters, 284 chippers, and 39 grinders), the prevalence rate of the syndrome was 13.4% and for a reference group of 256 workers it was 1.6%. The prevalence rate of white finger in the four regions differed and was higher in northeast and north China than in south and middlewest China. This finding suggests that cold climate and humidity may be causative factors of the vibration syndrome.