Clonal T-large granular lymphocytes (LGL) in chronic relapsing-remitting and refractory immune thrombocytopenia Free

Background Adult chronic immune thrombocytopenia (ITP)is a disease associated with a history of recurrent relapses and subsequent remissions further characterized by loss of response to previously effective treatment. Many of such treatments are directed toward reduction of autoantibody production and antibody mediated platelet clearance. However, recent reports support a role for T lymphocytes in refractory ITP patients. T-cell large granular lymphocytes, characterized as CD3, CD8, CD57 lymphocytes by flow cytometry and determined as clonal by T- cell receptor gene rearrangement have been reported in ITP patients. Beginning in 2020, peripheral blood smear analysis via Cellavison was made available to our hematologists along with CBC results. Review of lymphocyte populations allowed for rapid identification of LGL cells and immediate referral of the CBC specimen to flow analysis. We report here the first results of prospective study of LGL lymphocytes in patients with chronic ITP.

Methods On initial consultation of referred or newly diagnosed ITP patients by ASH and International guidelines all patient blood smears are reviewed on Cellavision version 7.1. During follow-up patient visits, blood smears are again reviewed at least twice a year. If greater that 2 LGL appearing lymphocytes are identified, the CBC specimen is sent to flow lab for analysis. A diagnosis of T-LGL lymphocytes is made when there were greater than 5% of T-lymphocytes, then a sample is sent for T cell receptor gene rearrangement. Patients continue follow-up and changes in T-LGL population is assessed at least once a year by flow cytometry.

Results Eleven patients (3 M/8 F) were identified by blood smear review followed by flow analysis and T receptor gene rearrangement as having a CD8, CD57+ clonal LGL population. The average patient age is 61yr (range: 23 yr -81 yr). The mean and median duration of ITP were 17yr and15 yr (Range: 2yr-46 yr). Nine were Primary ITP, two Secondary (RA, Lupus). LGL clone size at time of original diagnosis as % of T-cells averaged 15.1%, (Range: 7.8%-25.6%). On follow-up flow analysis, 7 patients had increases in their T-cell %. Five patients with clone sizes greater than 13.7% were screened and were negative for STAT 3 mutations. On T-cell receptor analysis, 7 patients were gamma/beta positive, two gamma positive only and one (the youngest) was gamma/delta positive. All patients had histories of multiple relapses and had received an average of 5 (range 4 to 7) therapies, with all having received steroids and TPO-R agonists. Only two patient had a splenectomy. Three highly refractory patients achieved a long term stable response with T cell directed therapy, 2 with sirolimus and 1 with cyclosporine. The patient with the longest disease history, post splenectomy and highly refractory required alemtuzumab to respond after a prolonged hospitalization due to platelet counts <5,000 and ongoing bleeding..

Conclusion In this ongoing study of LGL in patients with chronic ITP, the population described in this preliminary report had a more refractory clinical course with a history of multiple relapses while being treated with multiple therapies. The patients were older with a mean age of 61yrs with a prolonged clinical course. CD8, CD57 T-LGL cells are noted to be associated with significant cytopenia, such a pure red cell aplasia and severe neutropenia. A recent report documents the frequent finding of CD8 T-cell clones in ITP that expand as TEMRA cells in more refractory patients. The visual finding of LGL cells on blood smear review, confirmed by flow analysis and T cell receptor studies can provide the clinician with a clinical marker of a pathophysiologic and clinical transition in the ITP patient from disease dominated by antibody mediated platelet destruction with megakaryocyte injury to a disease dominated by cytotoxic T cell mediated platelet and megakaryocyte injury who is becoming refractory to antibody and B-cell targeted therapy. However, to recognize the emergence of these LGL would require ongoing regular review of peripheral blood smears beyond the initial diagnosis. This has not been recommended in guidelines. An alternate approach would be to perform lymphocyte flow analysis incorporating antibodies for CD57on patients who have become refractory to antibody and B-cell targeted therapies.