Recovery of KIR Expression After Allogeneic Stem Cell Transplantation in Multiple Myeloma Patients

Activating and inhibitory killer immunoglobulin like receptors (KIR) are predominantly expressed on natural killer (NK) cells. KIR mismatch allogeneic stem cell transplantation (alloSCT) has been reported to provide beneficial effects for Multiple Myeloma (MM). However, their recovery in MM patients remains poorly understood. We, therefore, analysed KIR recovery in 90 MM patients after alloSCT.

KIR expression (CD158a/h, CD158b/b2, CD158e1/e2) on NK cells and T cell subsets was measured by flow cytometry at different time points after alloSCT.

During the first 90 days after alloSCT NK cells represent the largest lymphocyte subset. Activating receptors like NKp30 and NKp44 showed a fluctuating expression while members of the KIR family were expressed at a constant rate (20% of NK cells). There was no significant difference in the early post transplantation period (day 0–90) compared to later time points (day 360).

In contrast, T cells showed increased KIR expression during the first 30 days after alloSCT, which was highly significant for CD158e (p=0,0001). After 30 days the expression declined to baseline. Furthermore, T cell activation marker HLA-DR reached its highest expression between days 60 and 90 when KIR receptors were expressed at their lowest level (27% vs. 8%, p < 0,0001).

We conclude that KIR receptors were differentially expressed on NK and T cells. Because KIR receptors are constantly expressed by NK cells and NK cells are the most frequent lymphocyte populations early after alloSCT, NK cells may be useful for KIR mismatch cellular therapy.

No relevant conflicts of interest to declare.