title: Visualizing CTL/melanoma cell interactions: multiple hits must be delivered for tumour cell annihilation.
abstract: It is well established that cytotoxic T lymphocytes (CTL) can kill target cells offering a very small number of specific peptide/MHC complexes (pMHC). It is also known that lethal hit delivery is a very rapid response that occurs within a few minutes after cell-cell contact. Whether cytotoxicity is efficient and rapid in the context of CTL interaction with target cells derived from solid tumours is still elusive. We addressed this question by visualizing the dynamics of human CTL interaction with melanoma cells and their efficiency in eliciting cytotoxicity. Our results show that in spite of CTL activation to lethal hit delivery, killing of melanoma cells is not efficient. Time-lapse microscopy experiments demonstrate that individual CTL rapidly polarize their lytic machinery towards target cells, yet the apoptotic process in melanoma cells is defective or 'delayed' as compared to conventional targets. These results indicate that although CTL activation to lethal hit delivery can be viewed as a 'digital' phenomenon rapidly triggered by a few ligands, melanoma cell annihilation is an 'analogue' response requiring multiple hits and prolonged contact time.
authors.affiliation: INSERM, Centre de Physiopathologie de Toulouse Purpan, Section Dynamique moléculaire des interactions lymphocytaires, Toulouse, France. icarama@igc.gulbenkiat.pt
authors.forename: Iris
authors.initials: I
authors.lastname: Caramalho
authors.forename: Mustapha
authors.initials: M
authors.lastname: Faroudi
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Padovan
authors.forename: Sabina
authors.initials: S
authors.lastname: Müller
authors.forename: Salvatore
authors.initials: S
authors.lastname: Valitutti
mesh_terms: D017209:Apoptosis; D049109:Cell Proliferation; D002469:Cell Separation; D003602:Cytotoxicity, Immunologic; D005434:Flow Cytometry; D005452:Fluoresceins / Q000737:chemistry; D007167:Immunotherapy / Q000379:methods*; D008024:Ligands; D058965:MART-1 Antigen / Q000096:biosynthesis; D008285:Major Histocompatibility Complex; D008545:Melanoma / Q000378:metabolism / Q000628:therapy*; D018613:Microscopy, Confocal / Q000379:methods; D010455:Peptides / Q000737:chemistry; D013602:T-Lymphocytes, Cytotoxic / Q000166:cytology* / Q000378:metabolism; D013997:Time Factors
chemical_list: D005452:Fluoresceins; D008024:Ligands; D058965:MART-1 Antigen; D010455:Peptides; C007740:fluorexon