Abstract Details

Title Dissection of the Distinct Susceptibility of Hematopoietic Precursors and Immune Cells to Cladribine

Topic Multiple Sclerosis

Presentation(s) P4 - Poster Session 4 (5:30 PM-6:30 PM)

Poster/Presentation
Number 15-045

Objective

To assess the enzymes involved in 2CdA metabolism in vitro in selected immature cells.

Background Cladribine (2CdA) is deoxyadenosine antimetabolite activated by sequential deoxycytidine kinase (dCK) phosphorylation causing cell death through apoptosis and necrosis. This is reverted by cytosolic 5’ deoxynucleotidase (NT5C2). Thus, high dCK/NT5C2 ratios in lymphocytes reflect 2CdA-specific lymphopenic effect. Clinical trials have shown a difference in timing of immunoreconstitution for different lymphocyte subsets in multiple sclerosis (MS) patients, suggesting that a differential susceptibility to 2CdA by these subsets and/or of their lymphoid progenitors is linked to dCK/NT5C2 ratio variability. Moreover, dCK expression and activity are enhanced during lymphopoiesis and in activated lymphocytes.

Design/Methods Hematopoietic stem cells, common lymphoid (CLP) and myeloid progenitor cells (CMP) from healthy donors were used in this investigation, as well as activated mature lymphoid and myeloid cellular subsets isolated from the peripheral blood of healthy donors upon 2CdA stimulation.

Results Flow cytometry analysis using pre-validated rabbit anti-dCK and anti-NT5C2 polyclonal antibodies showed a positive dCK/NT5C2 MFI ratio in B cells, T cells and monocytes, with mean values of 5.19, 3.28 and 2.17, respectively. Within B-cell subsets, dCK and NT5C2 expression was highly heterogeneous, with plasma cells displaying the highest MFI, but no significant differences were observed in the respective B-cell dCK/NT5C2 ratios (B memory dCK MFI mean = 10580, NT5C2 MFI mean = 3206, ratio = 3.30; B mature dCK MFI mean = 7496, NT5C2 MFI mean = 2356, ratio = 3.18; B transitional dCK MFI mean = 7364, NT5C2 MFI mean = 2451, ratio = 3.00; plasma cells dCK MFI mean = 16901, NT5C2 MFI mean = 2451, ratio = 2.47).

Conclusions These data support our suggestion that 2CdA affects specific immune cell subsets differentially.

Authors/Disclosures
PRESENTER	No disclosure on file
	No disclosure on file
	No disclosure on file
Ursula Boschert Shafaatian (C/o Serono)	Ursula Boschert has nothing to disclose.
	No disclosure on file
Antonio Uccelli, MD (Ospedale S. Martino - Genova)	An immediate family member of Dr. Uccelli has received personal compensation for serving as an employee of Biogen. The institution of Dr. Uccelli has received research support from Merck. The institution of Dr. Uccelli has received research support from Roche.

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