A Shift in the Phenotype of Melan-A-Specific CTL Identifies Melanoma Patients with an Active Tumor-Specific Immune Response

Abstract

In a significant proportion of melanoma patients, CTL specific for the melan-A26/7–35 epitope can be detected in peripheral blood using HLA-A2/peptide tetramers. However, the functional capacity of these CTL has been controversial, since although they prove to be effective killers after in vitro expansion, in some patients they have blunted activation responses ex vivo. We used phenotypic markers to characterize melan-A tetramer+ cells in both normal individuals and melanoma patients, and correlated these markers with ex vivo assays of CTL function. Melanoma patients with detectable melan-A tetramer+ cells in peripheral blood fell into two groups. Seven of thirteen patients had a CCR7+ CD45R0− CD45RA+ phenotype, the same as that found in some healthy controls, and this phenotype was associated with a lack of response to melan-A peptide ex vivo. In the remaining six patients, melan-A tetramer+ cells were shifted toward a CCR7− CD45R0+ CD45RA− phenotype, and responses to melan-A peptide could be readily demonstrated ex vivo. When lymph nodes infiltrated by melan-A-expressing melanoma cells were examined, a similar dichotomy emerged. These findings demonstrate that activation of melan-A-specific CTL occurs in only some patients with malignant melanoma, and that only patients with such active immune responses are capable of responding to Ag in ex vivo assays.

Qualitative difference between the cytotoxic T lymphocyte responses to melanocyte antigens in melanoma and vitiligo

“…By complementing the use of A2/Melan-A tetramers with both intracellular perforin staining and surface staining of memory/naivety markers, we found that the percentages of activated cells were also comparable. These observations are in agreement with previous literature data indicating that Melan-A-specific CTL from both melanoma and vitiligo patients frequently show signs of an in vivo antigen encounter [13,14,25,26], and indicate that the activation status of melanocyte-specific CTL is not a distinctive feature of either disease.…”

“…Second, we evaluated the response to the melanoma target in terms of TCR down-regulation. For this experiment, we chose the only melanoma patient whose PHA line exhibited some degree of TCR downregulation versus the natural Melan-A [26][27][28][29][30][31][32][33][34][35] peptide, a prerequisite for melanoma cell recognition, and we selected the vitiligo patient exhibiting the most similar behavior. The results indicated that only vitiligo CTL were capable of TCR down-regulation in response to this stimulus (Fig.…”

Ultra‐sensitive class I tetramer analysis reveals previously undetectable populations of antiviral CD8+ T cells

“…To ensure that this technique could be applied to the enrichment of such a T cell population, we used Melan-A-specific T cells. Phenotypic [12], functional [13] and molecular techniques [14] have confirmed unequivocally that in normal individuals, these T cells are truly antigen naive. Following enrichment, Melan-Aspecific T cells could be found at a frequency of 83.78% of CD8 + T cells (Fig.…”

HLA class II restricted T-cell receptor gene transfer generates CD4+ T cells with helper activity as well as cytotoxic capacity

“…T cells producing Th1 cytokines (IFNg and IL-2) have been shown to be responsible for antitumor reactivity. [33][34][35] Previously, we showed that HA-2-specific T cells isolated by tetramer during a strong GVL response produced large amounts of IFNg and no or low amounts of IL-4. 18 Furthermore, we recently demonstrated that T cells contributing to the GVL reactivity of DLI can be isolated based on their production of IFNg.…”