Differences in Granule Morphology yet Equally Impaired Exocytosis among Cytotoxic T Cells and NK Cells from Chediak–Higashi Syndrome Patients

Abstract

Chediak–Higashi syndrome (CHS) is caused by autosomal recessive mutations in LYST, resulting in enlarged lysosomal compartments in multiple cell types. CHS patients display oculocutaneous albinism and may develop life-threatening hemophagocytic lymphohistiocytosis (HLH). While NK cell-mediated cytotoxicity has been reported to be uniformly defective, variable defects in T cell-mediated cytotoxicity has been observed. The latter has been linked to the degree of HLH susceptibility. Since the discrepancies in NK cell- and T cell-mediated cellular cytotoxicity might result from differences in regulation of cytotoxic granule release, we here evaluated perforin-containing secretory lysosome size and number in freshly isolated lymphocytes from CHS patients and furthermore compared their exocytic capacities. Whereas NK cells from CHS patients generally contained a single, gigantic perforin-containing granule, cytotoxic T cells predominantly contained several smaller granules. Nonetheless, in a cohort of 21 CHS patients, cytotoxic T cell and NK cell granule exocytosis were similarly impaired upon activating receptor stimulation. Mechanistically, polarization of cytotoxic granules was defective in cytotoxic lymphocytes from CHS patients, with EEA1, a marker of early endosomes, mislocalizing to lysosomal structures. The results leads to the conclusion that lysosome enlargement corresponds to loss of distinct organelle identity in the endocytic pathway, which on a subcellular level more adversely affects NK cells than T cells. Hence, vesicular size or numbers do not per se dictate the impairment of lysosomal exocytosis in the two cell types studied.

Distinctive phenotypes and functions of innate lymphoid cells in human decidua during early pregnancy

“…The parallel increase in granule proteins and responsiveness to KIR cross linking as number of KIR increases, suggests a similar mechanism may operate in dNK. All these features of dNK granules resemble the pbNK from CHS patients that are poorly cytotoxic but maintain the capacity to produce cytokines 25,26,42 . The genetic mutation responsible for CHS affects the lysosomal trafficking regulator, LYST.…”

“…5g). Few large granules are characteristic of NK cells from CHS patients that are also poor killers 27 NATURE COMMUNICATIONS | https://doi.org/10.1038/s41467-019-14123-z ARTICLE cell granules are less clustered around the MTOC and we therefore measured this in dNK 25,27 . Analysis of dNK by confocal microscopy stained for LAMP-1/CD107a and pericentrin (an MTOC-associated protein) shows that dNK granules are further away from the MTOC compared to pbNK (Fig.…”

“…In pbNK from healthy individuals, cells with larger granules are not only better killers, but also produce more cytokines 24 . pbNK from patients with Chediak-Higashi syndrome (CHS) possess NK cells with fewer, larger granules that do not polarise towards canonical NK cell target cells compared to normal pbNK 25,26 . Despite this, their cytokine production is more efficient 27 .…”

The road to lysosome‐related organelles: Insights from Hermansky‐Pudlak syndrome and other rare diseases

“…Surviving patients suffer from a late‐onset neurological impairment . The symptoms reflect defects in lysosome and phagosome maturation, concomitant with the formation of giant enlarged lysosomes and LROs that cannot be secreted . The defective gene, LYST or CHS1, encodes a ~4000 amino acid protein with several identifiable protein domains including BEACH, pleckstrin homology, WD40 repeats, perilipin‐like, lectin‐like and HEAT/Armadillo‐like repeats .…”

Modulation of Secretory Lysosomes During NK Cell Education Leads to Accumulation of Granzyme B and Enhanced Functional Potential

“…76 NK cells in CHS patients are hyperresponsive and hypersecretory but are unable to degranulate. 77,78 Although NK cell activation followed by granule convergence and polarization appears to be normal in LYST-deficient NK cells, the enlarged granules fail to pass through the cortical actin meshwork openings at the immunological synapse. 36 By monitoring granule size and granzyme B density prior to and following degranulation, we observed a selective loss of the pre-converged, large dense-core granules after degranulation.…”