Intratumoral Cytotoxic T-Lymphocyte Density and PD-L1 Expression Are Prognostic Biomarkers for Patients with Colorectal Cancer.

Background and objectives: Cytotoxic T-lymphocyte (CTL)-mediated inflammatory response to tumors plays a crucial role in preventing the progression of some cancers. Programmed cell death ligand 1 (PD-L1), a cell-surface glycoprotein, has been reported to repress T-cell-mediated immune responses against tumors. However, the clinical significance of PD-L1 in colorectal cancer (CRC) remains unclear. Our aim was to elucidate the prognostic significance of PD-L1 expression and CD8+ CTL density in CRC. Materials and methods: CD8 and PD-L1 immunostaining was conducted on 157 pathologic specimens from patients with CRC. The CD8+ CTL density and PD-L1 expression within the tumor microenvironment were assessed by immunohistochemistry. Results: Tumor invasion (pT) was significantly correlated with intratumoral (p = 0.011) and peritumoral (p = 0.016) CD8+ CTLs density in the tumor microenvironment. In addition, there was a significant difference in the intensity of CD8+ CTLs between patients with and without distant metastases (intratumoral p = 0.007; peritumoral p = 0.037, T-test). Lymph node metastasis (pN) and TNM stage were significantly correlated with PD-L1 expression in CRC cells (p = 0.015, p = 0.029, respectively). Multivariate analysis revealed a statistically significant relationship between the intratumoral CD8+ CTL density and disease-free survival (DFS) (hazard ratio [HR] 2.06; 95% confidence interval [CI]: 1.01-4.23; p = 0.043). The DFS was considerably shorter in patients with a high expression of PD-L1 in cancer cells than those with a low expression (univariate HR 2.55; 95% CI 1.50-4.34; p = 0.001; multivariate HR 0.48; 95% CI 0.28-0.82; p = 0.007). Conversely, patients with high PD-L1 expression in tumor-infiltrating lymphocytes had a longer DFS in both univariate analysis (HR 0.25; 95% CI: 0.14-0.44; p < 0.001) and multivariate analysis (HR 3.42; 95% CI: 1.95-6.01; p < 0.001). Conclusion: The CD8+ CTL density and PD-L1 expression are prognostic biomarkers for the survival of patients with CRC.

Maximal exercise increases mucosal associated invariant T cell frequency and number in healthy young men.

PURPOSE: Mucosal associated invariant T (MAIT) cells have properties of the innate and acquired immune systems. While the response to vigorous exercise has been established for most leukocytes, MAIT cells have not been investigated. Therefore, the purpose was to determine if MAIT cell lymphocytosis occurs with acute maximal aerobic exercise and if this response is influenced by exercise duration, cardiovascular fitness, or body composition. METHODS: Twenty healthy young males with moderate fitness levels performed an extended graded exercise test until volitional fatigue. Peripheral blood mononuclear cells were isolated from venous blood obtained prior and immediately after exercise and were labeled to identify specific T cell populations using flow cytometry. RESULTS: The percentage of MAIT cells relative to total T cells significantly increased from 3.0 to 3.8% and absolute MAIT cell counts increased by 2.2-fold following maximal exercise. MAIT cell subpopulation proportions were unchanged with exercise. Within cytotoxic T lymphocytes (CTL), MAIT cells consisted of 8% of these cells and this remained constant after exercise. MAIT cell counts and changes with exercise were not affected by body composition, VO2peak, or exercise duration. CONCLUSIONS: Maximal exercise doubled MAIT cell numbers and showed preferential mobilization within total T cells but the response was not influenced by fitness levels, exercise duration, or body composition. These results suggest that acute exercise could be used to offset MAIT cell deficiencies observed with certain pathologies. MAIT cells also make up a substantial proportion of CTLs, which may have implications for cytotoxicity assays using these cells.

Classification of human natural killer cells based on migration behavior and cytotoxic response.

Despite intense scrutiny of the molecular interactions between natural killer (NK) and target cells, few studies have been devoted to dissection of the basic functional heterogeneity in individual NK cell behavior. Using a microchip-based, time-lapse imaging approach allowing the entire contact history of each NK cell to be recorded, in the present study, we were able to quantify how the cytotoxic response varied between individual NK cells. Strikingly, approximately half of the NK cells did not kill any target cells at all, whereas a minority of NK cells was responsible for a majority of the target cell deaths. These dynamic cytotoxicity data allowed categorization of NK cells into 5 distinct classes. A small but particularly active subclass of NK cells killed several target cells in a consecutive fashion. These "serial killers" delivered their lytic hits faster and induced faster target cell death than other NK cells. Fast, necrotic target cell death was correlated with the amount of perforin released by the NK cells. Our data are consistent with a model in which a small fraction of NK cells drives tumor elimination and inflammation.

Identification of swine influenza virus epitopes and analysis of multiple specificities expressed by cytotoxic T cell subsets.

BACKGROUND: Major histocompatibility complex (MHC) class I peptide binding and presentation are essential for antigen-specific activation of cytotoxic T lymphocytes (CTLs) and swine MHC class I molecules, also termed swine leukocyte antigens (SLA), thus play a crucial role in the process that leads to elimination of viruses such as swine influenza virus (SwIV). This study describes the identification of SLA-presented peptide epitopes that are targets for a swine CTL response, and further analyses multiple specificities expressed by SwIV activated CTL subsets. FINDINGS: Four SwIV derived peptides were identified as T cell epitopes using fluorescent influenza:SLA tetramers. In addition, multiple CTL specificities were analyzed using peptide sequence substitutions in two of the four epitope candidates analyzed. Interestingly both conserved and substituted peptides were found to stain the CD4-CD8+ T cell subsets indicating multiple specificities. CONCLUSIONS: This study describes a timely and cost-effective approach for viral epitope identification in livestock animals. Analysis of T cell subsets showed multiple specificities suggesting SLA-bound epitope recognition of different conformations.

Indoleamine 2,3-dioxygenase specific, cytotoxic T cells as immune regulators.

Indoleamine 2,3-dioxygenase (IDO) is an immunoregulatory enzyme that is implicated in suppressing T-cell immunity in normal and pathologic settings. Here, we describe that spontaneous cytotoxic T-cell reactivity against IDO exists not only in patients with cancer but also in healthy persons. We show that the presence of such IDO-specific CD8(+) T cells boosted T-cell immunity against viral or tumor-associated antigens by eliminating IDO(+) suppressive cells. This had profound effects on the balance between interleukin-17 (IL-17)-producing CD4(+) T cells and regulatory T cells. Furthermore, this caused an increase in the production of the proinflammatory cytokines IL-6 and tumor necrosis factor-α while decreasing the IL-10 production. Finally, the addition of IDO-inducing agents (ie, the TLR9 ligand cytosine-phosphate-guanosine, soluble cytotoxic T lymphocyte-associated antigen 4, or interferon γ) induced IDO-specific T cells among peripheral blood mononuclear cells from patients with cancer as well as healthy donors. In the clinical setting, IDO may serve as an important and widely applicable target for immunotherapeutic strategies in which IDO plays a significant regulatory role. We describe for the first time effector T cells with a general regulatory function that may play a vital role for the mounting or maintaining of an effective adaptive immune response. We suggest terming such effector T cells "supporter T cells."

Ex vivo identification, isolation and analysis of tumor-cytolytic T cells.

We isolated pure, viable populations of tumor-cytolytic T cells directly from patient blood samples using flow cytometric quantification of the surface mobilization of CD107a-an integral membrane protein in cytolytic granules-as a marker for degranulation after tumor stimulation. We show that tumor-cytolytic T cells are indeed elicited in patients after cancer vaccination, and that tumor reactivity is strongly correlated with efficient T-cell recognition of peptide-bearing targets. We combined CD107a mobilization with peptide-major histocompatibility complex (P-MHC) tetramer staining to directly correlate antigen specificity and cytolytic ability on a single-cell level. This showed that tumor-cytolytic T cells with high recognition efficiency represent only a minority of peptide-specific T cells elicited in patients after heteroclitic peptide vaccination. We were also able to expand these cells to high numbers ex vivo while maintaining their cytolytic potential. These techniques will be useful not only for immune monitoring of cancer vaccine trials, but also for adoptive cellular immunotherapy after ex vivo expansion. The ability to rapidly identify and isolate tumor-cytolytic T cells would be very useful in cancer immunotherapy.

Helper cell-independent cytotoxic clones in man.

We report here a class of helper cell-independent cytotoxic T cell (HITc) clones in man that can proliferate in response to antigenic stimulation as well as mediate cytotoxicity. HITc appear to be rare among clones derived from primary in vitro allosensitized culture, but constitute the majority of clones derived from cells sensitized to autologous Epstein-Barr virus-transformed lymphoblastoid cell lines. The implications of the derivation and function of HITc clones are discussed.

Human cytotoxic T lymphocytes evoked by group A streptococcal M proteins.

Purified group A streptococcal M proteins were used to stimulate peripheral blood lymphocytes from normal adult volunteers. The activated lymphocytes were cytotoxic against cultured human heart cells, as well as liver cells, fibroblasts, and K562 cells, but showed only minimal cytotoxicity against several animal cell types. The cytotoxic activity evoked by type 5 M protein was dose and time dependent. Rabbit antisera against pep M5 that contained heart-crossreactive antibodies partially inhibited cytotoxicity against heart cells, but had no effect on other target cells, suggesting that a fraction of the effector lymphocytes may be recognizing M protein-crossreactive cell surface antigens. All of the cytotoxic activity was recovered from a CD3+ population of lymphocytes obtained from a fluorescence-activated cell sorter, and CD4+ and CD8+ cells were also cytotoxic. M protein-responsive T cell clones were generated that showed specificity for heart and K562 cells, in addition to clones that were cytotoxic against both cell lines. Our data show that streptococcal M protein evokes cytotoxic T lymphocytes against multiple human but not animal target cells. Some of the effector cells may be specific for cultured myocardial cells, but their role in the pathogenesis of rheumatic carditis will require further studies of lymphocytes from patients with acute rheumatic fever and carditis.

Ontogeny of the Thy-1-, Lyt-2+ murine intestinal intraepithelial lymphocyte. Characterization of a unique population of thymus-independent cytotoxic effector cells in the intestinal mucosa.

Murine intestinal intraepithelial lymphocytes (IEL) from unprimed thymus-bearing and athymic nude mice were characterized according to the expression of murine lymphocyte antigenic markers and cytotoxic activity. The majority of IEL from thymus-bearing mice were Lyt-2+, L3T4- lymphocytes, over half of which did not express Thy-1 surface antigens. Nude IEL and spleen cells were void of Thy-1+ cells; however, Lyt-2 antigens were expressed on a significant proportion of IEL, but not splenic lymphocytes. Overall, 40-70% of IEL from either thymus-bearing or athymic mice expressed the cytotoxic activation antigen, CT-1, and the J11d lymphocyte marker, both of which were associated with a population of Thy-1-, Lyt-2+ cytotoxic IEL. These data are taken to mean that the intestinal epithelium is a site uniquely enriched for activated cytotoxic cells, a significant proportion of which originate as non-thymus-derived lymphocytes with acquired lytic activity.

Functional properties of a unique subset of cytotoxic CD3+ T lymphocytes that express Fc receptors for IgG (CD16/Leu-11 antigen).

A subset of peripheral blood T lymphocytes coexpressing CD3 and IgG Fc receptors (FcR) (CD16/Leu-11 antigen) have been identified, isolated, and functionally characterized. The CD3+, CD16+ cells were established in short-term culture using growth medium containing interleukin 2 (IL-2). Both the freshly isolated cells and the cultured cell line stably expressed the CD3+, CD16+ phenotype. Furthermore, a majority of these T cells lacked either CD4 or CD8 expression. Like in vitro-activated cytotoxic T lymphocytes and natural killer (NK) cells, the CD3+, CD16+ cells showed numerous azurophilic granules. Although these cells failed to mediate significant levels of NK cell-mediated cytotoxicity even after stimulation with IL-2, they efficiently functioned as effectors of antibody-dependent cellular cytotoxicity (ADCC). The Ig isotype specificity of the ADCC was analyzed using an isotype switch-variant family of a murine anti-HLA monoclonal antibody (mAb). Similar to the CD3-, CD16+ NK cell population, the CD3+, CD16+ T cells preferentially used the IgG2a antibody to mediate ADCC. The CD3+, CD16+ cells demonstrated a proliferative response when cocultured with either a NK-sensitive tumor cell line, K562, or a NK-insensitive B lymphoblastoid cell line, CCRF-SB. The response against CCRF-SB was significantly inhibited by anti-IL-2 receptor antibody, whereas the response against K562 was only partially diminished. Cytotoxicity was also induced in the CD3+, CD16+ population by the presence of anti-CD3 mAb, indicating that cytotoxicity can be triggered by stimulation via the CD3-T cell antigen receptor complex. By isolating these CD3+, CD16+ cells from the peripheral blood of a normal, healthy individual, it has been possible to extensively study the morphology, antigenic phenotype, and functional behavior of this unique subset of T lymphocytes expressing IgG FcR.

Properties of purified T cell subsets. I. In vitro responses to class I vs. class II H-2 alloantigens.

In light of the widely accepted view that Ia-restricted L3T4+ T helper cells play a decisive role in controlling the differentiation of Lyt-2+ cells, experiments were designed to examine whether Lyt-2+ cells can respond to antigen in the absence of L3T4+ cells. The results showed that highly purified Lyt-2+ cells gave high primary mixed lymphocyte reactions (MLR) to various class I differences, including both mutant and allelic differences; responses to class II (Ia) differences were generally undetectable with Lyt-2+ cells. The intensity of MLR to class I differences was not affected by addition of anti-L3T4 monoclonal antibodies (mAb) to the cultures or by removing T cells from the stimulator populations. Negative selection experiments showed that Lyt-2+ cells could respond to class I differences across Ia barriers. MLR of purified Lyt-2+ cells peaked on days 3-4 and then fell sharply; background responses with syngeneic stimulators (auto-MLR) were virtually absent. Parallel experiments with purified L3T4+ cells showed that this subset responded in MLR only to class II (Ia) and not class I differences, reached peak responses only on day 6 rather than days 3-4, and often gave high auto-MLR. Within the first 3-4 d of culture, MLR were generally higher with Lyt-2+ cells than L3T4+ cells. Although no evidence could be found that Ia-restricted L3T4+ cells were required for the response of Lyt-2+ cells, presentation of antigen by Ia+ cells appeared to be essential. Thus, responses were ablated by pretreating stimulator cells with anti-Ia mAb plus C'. Significantly the failure of Lyt-2+ cells to respond to anti-Ia plus C'-treated stimulators could not be restored by adding syngeneic spleen cells; addition of IL-2 led to only a minor (15%) restoration of the response. It is suggested that Ia+ cells provide an obligatory second signal required by Lyt-2+ cells.

Quantitative assessment of the pool size and subset distribution of cytolytic T lymphocytes within human resting or alloactivated peripheral blood T cell populations.

In order to directly assess the distribution of cytolytic T lymphocytes (CTL) and their precursors (CTL-P) in the two major subsets of human T cells, we have used limiting dilution microculture systems to determine their frequencies. The two subsets were defined according to their reactivity (or lack thereof) with B9.4 monoclonal antibody (the specificity of which is similar, if not identical, to that of Leu 2b monoclonal antibody). Both B9+ and B9- cells obtained by sorting peripheral blood resting T cells using the fluorescence-activated cell sorter (FACS) were assayed for total CTL-P frequencies in a microculture system that allows clonal growth of every T cell. As assessed by a lectin-dependent assay, approximately 30% of peripheral blood T cells were CTP-P. In the B9+ subset (which represents 20-30% of all T cells), the CTL-P frequency was close to 100%, whereas the B9- subset had a 25-fold lower CTL-P frequency. It is thus evident that 90% and 10% of the total CTL-P in peripheral blood are confined to the B9+ or B9- T cell subsets, respectively. Analysis of the subset distribution of CTL-P directed against a given set of alloantigens confirmed these findings. CTL-P frequencies were also determined in B9+ and B9- subsets derived from T cells that had been activated in allogenic mixed leucocyte cultures (MLC). Approximately 10% of MLC T cells were CTL-P. This frequency was increased 3.5-fold in the B9+ subset, whereas the B9- subset contained only a small, although detectable number of CTL-P. Moreover, the great majority of the (operationally defined) CTL-P in MLC T cell population were found to be directed against the stimulating alloantigens, thus indicating a dramatic increase in specific CTL-P frequencies following in vitro stimulation in bulk cultures.

Cellular requirements for renal allograft rejection in the athymic nude rat.

This study has examined the ability of adoptively transferred CD4+ and CD8+ T cells to mediate rejection of a fully allogeneic DA renal graft in the PVG nude rat. Transfer, at the time of transplantation, of naive CD4+ T cells caused rapid graft rejection and primed CD4+ cells were several times more potent. In contrast, naive or specifically sensitized CD8+ cells were entirely ineffective at mediating renal allograft rejection. Whereas nonrejecting grafts showed only a mild cellular infiltrate, rejecting grafts in CD4+ reconstituted animals showed a substantial infiltrate and many of the infiltrating cells had a phenotype (MRC OX8+, MRC OX19-), consistent with NK cells. Experiments using a mAb (HIS 41) against an allotypic determinant of the leukocyte common antigen confirmed that the majority (greater than 80%) of the cellular infiltrate in rejecting grafts derived from the host rather than from the CD4+ inoculum. Infiltrating mononuclear cells, obtained from rejecting allografts 7 d after transplantation in CD4+-injected PVG nude hosts, showed high levels of in vitro cytotoxicity against not only kidney donor strain Con A blasts but also third-party allogeneic Con A blasts, as well as against both NK and LAK susceptible targets. When splenocytes from nontransplanted nude PVG rats were tested in vitro they also demonstrated high levels of lytic activity against both NK and LAK susceptible targets as well as allogeneic Con A blasts, which were not susceptible to lysis by spleen cells from euthymic rats. These findings suggest that injected CD4+ cells may cause renal allograft rejection by the recruitment of extrathymically derived, widely alloreactive cells into the kidney in this model of graft rejection.

A high proportion of T lymphocytes that infiltrate H-2-incompatible heart allografts in vivo express genes encoding cytotoxic cell-specific serine proteases, but do not express the MEL-14-defined lymph node homing receptor.

The role of cytotoxic cells in in vivo immune functions such as allograft rejection is unknown. To begin to assess the function of cytolytic cells in vivo we have begun with cytolytic cell-specific functional molecules: we have isolated and characterized cytolytic cell-specific cDNA clones from cytolytic T cell clones, both encoding distinct serine esterases. The HF gene encodes a trypsin-like enzyme while the C11 gene encodes an enzyme with likely specificity for acidic residues. Here we demonstrate, using in situ hybridization with RNA probe, that both genes are expressed selectively in a subset of T lymphocytes that have infiltrated cardiac allografts. The phenotype of these cells is consistent with the most frequent phenotype of active CTL raised in vitro: they are predominantly CD4-, CD8+, MEL-14- T cell blasts. Thus the expression of these genes, each of which encodes serine esterase found in killer cell granules in vitro, is a valid marker for these cells in vivo as well. The kinetics of their accumulation is consistent with, but not proof of, a putative role in allograft rejection. It is likely that HF and C11 gene expression will be of diagnostic value.

T cell memory. Long-term persistence of virus-specific cytotoxic T cells.

This study documents that virus-specific CTL can persist indefinitely in vivo. This was accomplished by transferring Thy-1.1 T cells into Thy-1.2 recipient mice to specifically identify the donor T cell population and to characterize its antigenic specificity and function by using a virus-specific CTL assay. Thy-1.1+ T cells from mice previously immunized with lymphocytic choriomeningitis virus (LCMV) were transferred into Thy-1.2 mice persistently infected with LCMV. The transferred LCMV-specific CTL (Thy-1.1+ CD8+) eliminate virus from the chronically infected carriers and persist in the recipient mice in small numbers, comprising only a minor fraction of the total T cells. Upon re-exposure to virus, these long-lived "resting" CD8+ T cells proliferate in vivo to become the predominant cell population. These donor CD8+ T cells can be recovered up to a year post-transfer and still retain antigenic specificity and biological function. They kill LCMV infected H-2-matched cells in vitro and can eliminate virus upon transfer into a second infected host. In addition, these long-lived CD8+ T cells appear not to be dependent on help from CD4+ T cells, since depletion of CD4+ T cells has minimal or no effect on their biological properties (proliferation, CTL response, viral clearance). These donor CTL also exhibit an immunodominance over the host-derived LCMV-specific CTL response. When both host and donor T cells are present, the donor CTL response is dominant over the potential CTL response of the cured carrier host. Taken together, these results suggest that virus-specific CTL can persist for the life span of the host as memory cells.

Cytotoxic T lymphocyte recognition of the influenza hemagglutinin gene product expressed by DNA-mediated gene transfer.

We have used the technique of DNA-mediated gene transfer to examine cytotoxic T lymphocyte (CTL) recognition of the product of the cloned A/JAPAN/305/57 hemagglutinin (HA) gene in murine (L929) cells. Using both heterogeneous and homogeneous (clonal) populations of type A influenza-specific CTL, we have demonstrated that the HA molecule can serve as a target antigen for both the subtype-specific and the cross-reactive subpopulations of influenza-specific CTL. Our results also raise the possibility that other virus-specified polypeptides may serve as target molecules for cross-reactive CTL.

Clonal heterogeneity in the requirement for T3, T4, and T8 molecules in human cytolytic T lymphocyte function.

In an attempt to define the requirement of T8, T4, and T3 surface molecules in functional interactions occurring between human cytolytic T lymphocytes (CTL) and specific target cells, we have analyzed a large number of CTL clones derived from primary mixed lymphocyte culture (MLC) T cell populations for their susceptibility to inhibition by monoclonal antibodies (mAb) directed against these surface antigens. In most experiments, MLC T cells were stained with B9.4 (anti-T8) or OKT4 (anti-T4) mAb, separated into positive and negative cells using a fluorescence-activated cell sorter (FACS) and cloned under limiting conditions. While the lytic activity of the majority of T8+ CTL clones was inhibited by B9.4 mAb, approximately 15% of these clones were unaffected even in the presence of excess antibody. Flow cytofluorometric analysis of T8 antigen in individual clones did not show any correlation between the amount of T8 antigen expressed, the magnitude of cytolytic activity and the susceptibility (or lack thereof) to inhibition by B9.4 mAb. Of the 16 T4+ CTL clones analyzed, 7 were resistant to inhibition by OKT4 mAb even at doses 10-fold higher than that sufficient for complete inhibition of susceptible clones. Again, no correlation was found between the amount of T4 antigen expressed and the susceptibility to inhibition by the corresponding antibody. The same sets of T8+ and T4+ CTL clones were also analyzed for their susceptibility to inhibition by OKT3 mAb. Although all of the clones expressed the T3 surface antigen, only 15/23 T8+ clones and 9/14 T4+ clones were inhibited by anti-T3 mAb. To further document this clonal heterogeneity, we selected two T3+ T4- T8+ CTL clones that had no concomitant NK-like activity. One clone was resistant to inhibition by OKT3 mAb, whereas the other was highly susceptible. Incubation with OKT3 mAb resulted in modulation of the T3 molecules in both clones. Following modulation, however, the cytolytic activity of the resistant clones was unaffected, whereas the lytic activity of the susceptible clone was abrogated. These results thus indicate extensive clonal heterogeneity in the requirement for T3, T4, and T8 molecules in CTL function. Moreover, it appears that T3 molecules are not always physically and functionally linked to CTL receptor structures.

The influenza A virus nucleoprotein gene controls the induction of both subtype specific and cross-reactive cytotoxic T cells.

Using genetically typed recombinant influenza A viruses that differ only in their genes for nucleoprotein, we have demonstrated that repeated stimulation in vitro of C57BL/6 spleen cells primed in vivo with E61-13-H17 (H3N2) virus results in the selection of a population of cytotoxic T lymphocytes (CTL) whose recognition of infected target cells maps to the gene for nucleoprotein of the 1968 virus. Influenza A viruses isolated between 1934 and 1979 fall into two groups defined by their ability to sensitize target cells for lysis by these CTL: 1934-1943 form one group (A/PR/8/34 related) and 1946-1979 form the second group (A/HK/8/68 related). These findings complement and extend our previous results with an isolated CTL clone with specificity for the 1934 nucleoprotein (27, 28). It is also shown that the same spleen cells derived from mice primed with E61-13-H17 virus in vivo, but maintained in identical conditions by stimulation with X31 virus (which differs from the former only in the origin of its gene for NP) in vitro, results in the selection of CTL that cross-react on target cells infected with A/PR/8/1934 (H1N1) or A/Aichi/1968 (H3N2). These results show that the influenza A virus gene for NP can play a role in selecting CTL with different specificities and implicate the NP molecule as a candidate for a target structure recognized by both subtype-directed and cross-reactive influenza A-specific cytotoxic T cells.

Phenotypic and functional separation of memory and effector human CD8+ T cells.

Human CD8+ memory- and effector-type T cells are poorly defined. We show here that, next to a naive compartment, two discrete primed subpopulations can be found within the circulating human CD8+ T cell subset. First, CD45RA-CD45R0(+) cells are reminiscent of memory-type T cells in that they express elevated levels of CD95 (Fas) and the integrin family members CD11a, CD18, CD29, CD49d, and CD49e, compared to naive CD8+ T cells, and are able to secrete not only interleukin (IL) 2 but also interferon gamma, tumor necrosis factor alpha, and IL-4. This subset does not exert cytolytic activity without prior in vitro stimulation but does contain virus-specific cytotoxic T lymphocyte (CTL) precursors. A second primed population is characterized by CD45RA expression with concomitant absence of expression of the costimulatory molecules CD27 and CD28. The CD8+CD45RA+CD27- population contains T cells expressing high levels of CD11a, CD11b, CD18, and CD49d, whereas CD62L (L-selectin) is not expressed. These T cells do not secrete IL-2 or -4 but can produce IFN-gamma and TNF-alpha. In accordance with this finding, cells contained within this subpopulation depend for proliferation on exogenous growth factors such as IL-2 and -15. Interestingly, CD8+CD45RA+CD27- cells parallel effector CTLs, as they abundantly express Fas-ligand mRNA, contain perforin and granzyme B, and have high cytolytic activity without in vitro prestimulation. Based on both phenotypic and functional properties, we conclude that memory- and effector-type T cells can be separated as distinct entities within the human CD8+ T cell subset.

Melanocyte destruction after antigen-specific immunotherapy of melanoma: direct evidence of t cell-mediated vitiligo.

Current strategies for the immunotherapy of melanoma include augmentation of the immune response to tumor antigens represented by melanosomal proteins such as tyrosinase, gp100, and MART-1. The possibility that intentional targeting of tumor antigens representing normal proteins can result in autoimmune toxicity has been postulated but never demonstrated previously in humans. In this study, we describe a patient with metastatic melanoma who developed inflammatory lesions circumscribing pigmented areas of skin after an infusion of MART-1-specific CD8(+) T cell clones. Analysis of the infiltrating lymphocytes in skin and tumor biopsies using T cell-specific peptide-major histocompatibility complex tetramers demonstrated a localized predominance of MART-1-specific CD8(+) T cells (>28% of all CD8 T cells) that was identical to the infused clones (as confirmed by sequencing of the complementarity-determining region 3). In contrast to skin biopsies obtained from the patient before T cell infusion, postinfusion biopsies demonstrated loss of MART-1 expression, evidence of melanocyte damage, and the complete absence of melanocytes in affected regions of the skin. This study provides, for the first time, direct evidence in humans that antigen-specific immunotherapy can target not only antigen-positive tumor cells in vivo but also normal tissues expressing the shared tumor antigen.