Endocrine Abstracts

Objectives: The treatment of active moderate-to-severe Thyroid Eye Disease (TED) consists of intravenous methylprednisolone (ivMP) as first-line, and several other immunosuppressants as second-line, including tocilizumab (TCZ) and rituximab (RTX), two humanized antibodies targeting IL6-receptor and CD20, respectively. The characterization of target-tissue-resident lymphocyte subpopulations before and after treatment might help to personalise TED treatment, by elucidating the different mechanisms of action.

Methods: Lymphocytes were derived from blood and paired ultrasound-guided fine-needle aspiration (US-FNA) of thyroid and neck lymph nodes (LNs) in 8 patients with moderate-to-severe active TED at two time-points: before and a mean of 5 months after TED treatment: ivMP (n = 3), TCZ (n = 3) and RTX (n = 2). The obtained lymphocytes were analysed with two techniques: 1) characterization of T and B lymphocyte subpopulations by flow cytometry immunophenotyping with a 21 surface/intracellular staining panel; 2) detection of intracellular cytokines and T-cell early-activation markers CD69 and CD40L (CD154), induced on T cells during lymphoid activation. The interaction between CD40, expressed on the surface of B lymphocytes, and CD40L is involved in B-cell activation and differentiation in memory cells.

Results: TCZ and ivMP did not induce significant changes of T and B lymphocyte subpopulations in blood, thyroid or LNs. In contrast, RTX induced depletion of CD19+ B cells in all three target depots, associated with a reduction of follicular helper T cells (Tfh) in LNs in one patient, while immunophenotyping of the second patient treated with RTX is ongoing. CD69 and CD40L blood-expression were decreased after TCZ and RTX therapy, but not after IvMP. CD69 and CD40L expression analysis within LNs was available in one patient treated with RTX, and was also decreased post-treatment.

Conclusions: Our preliminary results show that both TCZ and RTX, both not ivMP, induced a reduction of CD69 and CD40L T-cell activation markers, suggesting a specific effect on T-cell antigen presentation and B-cell co-stimulation. As expected RTX, and not TCZ or ivMP, also acts as B-cell depleting agent. LNs and thyroid US-FNA is a well tolerated and repeatable technique, allowing the analysis of tissue-resident lymphocytes pre- and post-immunotherapy. We are currently increasing the number of patients analysed pre- and post- immunotherapy for TED, to elucidate the mechanisms of action and potentially guide in the choice of TED treatment.