Cord blood nucleated cells induce delayed T cell alloreactivity

Area of Science:

• Immunology
• Hematology
• Transplantation Biology

Background:

• Cord blood (CB) mononuclear cells (MNCs) are used in transplants, even with HLA mismatches, showing limited graft rejection and graft-versus-host disease (GVHD).
• Previous research indicates CB contains naive T cells and hyporesponsive dendritic cells.

Purpose of the Study:

• To investigate the antigen-presenting cell (APC) capacity of CB MNCs in allogeneic T cell responses.
• To understand the potential mechanisms behind limited GVHD and graft rejection in CB transplantation.

Main Methods:

• Standard in vitro assays, including primary and secondary mixed lymphocyte cultures (MLC).
• Analysis of T cell proliferation and cytotoxic responses.
• Assessment of APC activity using purified CD34(+) cells, CD14(+) monocytes, and CB-derived immature monocyte-derived dendritic cells (iMo-DCs).

Main Results:

• CB MNCs did not stimulate allogeneic T cell proliferation or cytotoxicity in primary MLC.
• CB MNCs did not suppress T cell responses; purified cells showed normal responses when CB MNCs were added back.
• T cells stimulated with CB CD34(+) cells or iMo-DCs in secondary MLC showed potent proliferative responses.
• Delayed APC activity was observed after 6 days of stimulation, with upregulation of CD86 and HLA-DR on CB cells.
• Cytotoxic lymphocytes (CTLs) were generated after prolonged stimulation with CB MNCs or CB-derived iMo-DCs.

Conclusions:

• CB MNCs exhibit delayed APC activity, which can be enhanced after stimulation.
• This delayed APC function may play a role in mitigating early graft rejection and GVHD.
• The findings suggest that CB APCs may mature post-transplant, contributing to immune tolerance or delayed immune responses.