Multiple myeloma (MM) is a B cell haematological cancer which remains largely incurable. We have found that unconventional T cells (natural killer T cells and mucosal associated invariant T cells) show alterations in frequency and function in MM. Specifically the frequency of MAIT cells in the peripheral blood of patients with MM and its pre-malignant phase (P<0.001) is significantly reduced when compared to healthy donors. Due to the influential regulatory role played by these cell types, these alterations may contribute to disease progression. In order to better understand the changes in these cells evident in MM we are investigating the differential effects that antigen presenting cells (APC) (B cells, dendritic cells and macrophages) have on the functional differentiation of unconventional T cell responses. This study will characterise the functional responses of MAIT cells and NKT cells, when activated by various types of APC, in both healthy individuals, and patients with MM. We hypothesise that the malignant B cells in MM may act as abnormal APC thereby contributing to the alteration in unconventional T cell function in patients with MM and potentially playing a role in disease progression.