Research ResourceImmunology

Measurement of leukocyte trafficking kinetics in macaques by serial intravascular staining

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Science Translational Medicine  13 Jan 2021:
Vol. 13, Issue 576, eabb4582
DOI: 10.1126/scitranslmed.abb4582

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SIVSing through GVHD

Currently, there are few ways to track leukocyte movements in vivo. Potter and colleagues developed a method to track leukocyte migration in vivo called serial intravascular staining or SIVS. The authors infused differently labeled antibodies at different time points to reveal distinct leukocyte population kinetics in healthy macaques and those infected with Mycobacterium tuberculosis. Tkachev et al. then applied SIVS to shed light on donor T cell trafficking in macaques that developed acute graft-versus-host disease (GVHD) after transplant. They found that donor cytotoxic CD8+ T cells infiltrated the gastrointestinal tract and developed the transcriptional signature of tissue-resident memory T cells. SIVS will be useful for revealing leukocyte trafficking kinetics not only in GVHD and infection but in a variety of other diseases as well.

Abstract

Leukocyte trafficking enables detection of pathogens, immune responses, and immune memory. Dysregulation of leukocyte trafficking is often found in disease, highlighting its important role in homeostasis and the immune response. Whereas some of the molecular mechanisms mediating leukocyte trafficking are understood, little is known about the regulation of trafficking, including trafficking kinetics and its impact on immune homeostasis. We developed a method of serial intravascular staining (SIVS) to measure trafficking kinetics in nonhuman primates using infusions of fluorescently labeled antibodies to label circulating leukocytes. Because antibody infusions labeled only leukocytes in the blood, cells were “barcoded” according to their location at the time of each infusion, providing positional histories that could be used to infer trafficking kinetics. We used SIVS and multiparameter flow cytometry to quantitate cellular trafficking into lymphoid tissues of healthy animals at homeostasis and to identify perivascular cells that could be unique to nonlymphoid organs. To investigate how these parameters could be influenced during disease, SIVS was used to quantify lymphocyte trafficking in macaques infected with the bacterial pathogen Mycobacterium tuberculosis and to enumerate intravascular leukocytes in lung granulomas. We showed that whereas most cells in lung granulomas were localized there for more than 24 hours, granulomas were dynamic with a slow continual cellular influx, the rate of which predicted clearance of M. tuberculosis from the granulomas. SIVS, in combination with intracellular staining and multiparametric flow cytometry, is a powerful method to quantify the kinetics of leukocyte trafficking in nonhuman primates in vivo.

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