Heterogeneous binding and killing behaviour of human gamma/delta-TCR+ lymphokine-activated killer cells against K562 and Daudi cells

Extensive expansion of primary human gamma delta T cells generates cytotoxic effector memory cells that can be labeled with Feraheme for cellular MRI

Gamma delta T cells (GDTc) comprise a small subset of cytolytic T cells shown to kill malignant cells in vitro and in vivo. We have developed a novel protocol to expand GDTc from human blood whereby GDTc were initially expanded in the presence of alpha beta T cells (ABTc) that were then depleted prior to use. We achieved clinically relevant expansions of up to 18,485-fold total GDTc, with 18,849-fold expansion of the Vδ1 GDTc subset over 21 days. ABTc depletion yielded 88.1 ± 4.2 % GDTc purity, and GDTc continued to expand after separation. Immunophenotyping revealed that expanded GDTc were mostly CD27-CD45RA- and CD27-CD45RA+ effector memory cells. GDTc cytotoxicity against PC-3M prostate cancer, U87 glioblastoma and EM-2 leukemia cells was confirmed. Both expanded Vδ1 and Vδ2 GDTc were cytotoxic to PC-3M in a T cell antigen receptor- and CD18-dependent manner. We are the first to label GDTc with ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles for cellular MRI. Using protamine sulfate and magnetofection, we achieved up to 40 % labeling with clinically approved Feraheme (Ferumoxytol), as determined by enumeration of Perls' Prussian blue-stained cytospins. Electron microscopy at 2,800× magnification verified the presence of internalized clusters of iron oxide; however, high iron uptake correlated negatively with cell viability. We found improved USPIO uptake later in culture. MRI of GDTc in agarose phantoms was performed at 3 Tesla. The signal-to-noise ratios for unlabeled and labeled cells were 56 and 21, respectively. Thus, Feraheme-labeled GDTc could be readily detected in vitro via MRI.

Human Vδ1 γδ T cells expanded from peripheral blood exhibit specific cytotoxicity against B-cell chronic lymphocytic leukemia-derived cells

BACKGROUND AIMS

There is increasing interest in using γδ T cells (GDTC) for cancer immunotherapy. Most studies have been concerned with the Vδ2 subset in blood, for which several expansion protocols exist. We have developed a protocol to expand Vδ1 and Vδ2 preferentially from human blood. We have characterized these subsets and their specificities for leukemic targets.

METHODS

GDTC were isolated from the peripheral blood mononuclear cells (PBMC) of healthy donors via positive magnetic cell sorting; their proliferation in vitro was induced by exposure to the mitogen concanavalin A (Con A). CD107 and cytotoxicity (Cr(51)-release and flow cytometric) assays were performed. GDTC clones and target cells were immunophenotyped via flow cytometry.

RESULTS

Longer initial exposure to Con A typically resulted in higher Vδ1 prevalence. Vδ1 were activated by and cytotoxic to B-cell chronic lymphocytic leukemia (B-CLL)-derived MEC1 cells, whereas Vδ2 also responded to MEC1 but more so to the Philadelphia chromosome-positive [Ph+] leukemia cell line EM-enhanced green fluorescent protein (2eGFPluc). Vδ2 clone cytotoxicity against EM-2eGFPluc correlated with Vδ2 T-cell antigen receptor (TCR) and receptor found on Natural Killer cells and many T-cells (NKG2D), whereas Vδ1 clone cytotoxicity versus MEC1 correlated with Vδ1 TCR, CD56 and CD95 expression. Vδ1 also killed Epstein-Barr Virus (EBV)-negative B-CLL-derived TMD2 cells. Immunophenotyping revealed reduced HLA-ABC expression on EM-2eGFPluc, whereas MEC1 and TMD2 exhibited higher Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand (TRAILR1).

CONCLUSIONS

Our ability to expand peripheral Vδ1 cells and show their cytotoxicity to B-CLL-derived cell lines suggests that this novel approach to the cellular treatment of B-CLL may be feasible.

Anti-leukemia activity of in vitro-expanded human gamma delta T cells in a xenogeneic Ph+ leukemia model

Gamma delta T cells (GDTc) lyse a variety of hematological and solid tumour cells in vitro and in vivo, and are thus promising candidates for cellular immunotherapy. We have developed a protocol to expand human GDTc in vitro, yielding highly cytotoxic Vgamma9/Vdelta2 CD27/CD45RA double negative effector memory cells. These cells express CD16, CD45RO, CD56, CD95 and NKG2D. Flow cytometric, clonogenic, and chromium release assays confirmed their specific cytotoxicity against Ph(+) cell lines in vitro. We have generated a fluorescent and bioluminescent Ph(+) cell line, EM-2eGFPluc, and established a novel xenogeneic leukemia model. Intravenous injection of EM-2eGFPluc into NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ (NSG) mice resulted in significant dose-dependent bone marrow engraftment; lower levels engrafted in blood, lung, liver and spleen. In vitro-expanded human GDTc injected intraperitoneally were found at higher levels in blood and organs compared to those injected intravenously; GDTc survived at least 33 days post-injection. In therapy experiments, we documented decreased bone marrow leukemia burden in mice treated with GDTc. Live GDTc were found in spleen and bone marrow at endpoint, suggesting the potential usefulness of this therapy.

Autoimmune hair loss induced by alloantigen in C57BL/6 mice

Exponentially growing Meth-A cells expressing H-2K(d).D (d) antigen were found to induce alopecia when injected intraperitoneally into normal C57BL/6 mice, which express the H-2K(b).D (b) antigen. However, the capacity to induce alopecia disappeared when Meth-A cells were treated with K252a, which inhibits protein kinases. Histologically, skin in affected areas showed dense mononuclear cell infiltration and a focal foreign-body giant-cell reaction in hair follicles. The subtyping of lymphocytes in peripheral blood demonstrated a significant difference between normal mice and Meth-A cell-injected mice. To further examine the mechanism by which the alloantigen induces alopecia, lymphocytes isolated from the peripheral blood of normal C57BL/6 mice were cultured in medium containing Meth-A cell homogenate, phytohemagglutinin (PHA) and recombinant mouse interleukin-2 (rm IL-2), and intravenously injected into normal C57BL/6 mice. The adoptive transfer of the lymphocytes induced alopecia in a similar way. These findings suggest that the protein kinase-modulated alloantigen induces alopecia by disturbing the immunological homeostasis, and that lymphokine-activated killer cells play an important role in induction of alopecia by cross-reacting with hair follicles.

Human gamma delta T cells recognize heat shock protein-60 on oral tumor cells

In the present investigations, gammadelta T cells were isolated from the peripheral blood of oral cancer patients and analyzed for their immunophenotype and cytotoxic potential. Flow-cytometric analysis revealed a dominant population expressing Vgamma9 and Vdelta2 T-cell receptors. In a 4-hr 51Cr-release assay, activated gammadelta T cells showed specific cytotoxicity against Daudi Burkitt's lymphoma cells and fresh oral tumor cells. Cold target competition assays demonstrated that gammadelta T cells recognize a common ligand on Daudi and oral tumor cells. Expression of heat shock protein 60 (hsp60) molecules was detected on the surface of Daudi as well as oral tumor cells by flow cytometry and immunoprecipitation of surface biotinylated cells by anti-hsp60 monoclonal antibody (MAb). Such MAbs brought about a significant inhibition of cytotoxicity of gammadelta T cells against Daudi and oral tumor cells. The results suggest that gammadelta T cells isolated from the peripheral blood of oral cancer patients have the ability to lyse oral tumor cells. The lysis of oral tumor cells occurs via recognition of hsp60 on the surface of oral tumor cells.

Autologous mixed leucocyte reaction and the polyclonal activation of bovine gamma/delta T cells

Bovine gamma/delta T cells proliferate in response to stimulation with gamma-irradiated autologous monocytes in the autologous mixed leukocyte reaction (AMLR). Flow cytometric analyses indicated that the proliferating cells included three major subpopulations of bovine gamma/delta T cells, distinguished by the differential expression of the gamma/delta T cell receptor epitopes N6 and N7. Interleukin-2 and acid-labile interferon were produced in AMLR cultures but the cultured cells did not lyse any of a large variety of target cells, including monocytes, allogeneic lymphoblasts, transformed bovine B cells (BL3), bovine fibroblast and the natural killer cell targets D17 and K562, even in the presence of lectins or after co-stimulation in the AMLR with antibodies to WC1, the gamma/delta T cell lineage-specific cell-surface differentiation antigen. Ex vivo gamma/delta T cells did not display lymphokine-activated killing whereas populations of peripheral blood mononuclear cells containing alpha/beta T cells did.

Proliferation of IL-2 activated lymphocytes preferably occurs in aggregates by cells expressing the CD57 antigen

Aggregates of lymphocytes were investigated in long-term cultures of IL-2 stimulated peripheral blood mononuclear cells. Cells in clusters formed broad contact areas where coated pits and vesicles were often detectable. Proliferating cells were preferably found in aggregates indicating that the cell clusters represent proliferation centres in which cell division may be promoted by accessory signal transduction mediated by the close cell-to-cell contact. In bulk cultures CD57+ cells yielded increased proliferation capacity compared to CD57- cells. In addition, CD57+ cells were preferably localized in aggregates where they occupied the same position at the periphery of the clusters than the proliferating cells, suggesting that both cell types may be identical. It is discussed that the CD57 antigen represents a differentiation marker which is upregulated when CD57- cells start to proliferate assisted in cell aggregates.

Development of four donor-specific phenotypes in human long-term lymphokine-activated killer cell cultures

A series of 62 lymphokine-activated killer cell (LAK) cultures from 44 different donors was investigated for the distribution of various CD markers during a cultivation period of 3 weeks. Great differences in the phenotypic pattern were found between different donors, but similar changes of the subset pattern of various donors allowed a classification of the LAK cultures into four distinct LAK types. LAK type 1 was characterised by low numbers of CD3+ cells and high values for CD56+ cells. In LAK type 2 cultures gamma/delta TCR+ cells extensively proliferated, whereas in LAK type 3 cultures the CD57 and CD8 values increased considerably. LAK type 4 cultures did not show any of these characteristics. The resulting phenotype of a LAK culture was donor-specific, as LAK cultures established from the same peripheral blood mononuclear cells (PBMC), fresh or after cryopreservation, or from PBMC obtained from the same donor at different venous punctures, always developed the same phenotype. A clear correlation between phenotype and killing activity could only be found for LAK type 1 cultures, which always developed high lytic activity. Long-term IL-2 stimulation induced high levels of perforin-positive cells in LAK cultures but the perforin content did not correlate with the cytotoxicity. The transcription pattern for various cytokines only varied slightly between the cultures. Messenger RNA for granulocyte/macrophage- colony-stimulating factor, interferon gamma, tumour necrosis factor alpha, interleukin-4 (IL-4) and IL-5 were found in almost all cultures during the entire cultivation period, whereas mRNA for IL-2 was never detected. Most variations in the transcription pattern were observed for IL-6 and IL-7. However, no correlation could be found between the endogenous cytokine production and the phenotype or lytic activity of the LAK cultures. Further studies are required to determine the factors that cause lymphocyte subsets from a specific donor to proliferate preferentially under long-term IL-2 stimulation.