Belatacept suppresses B-cell subset alloresponses

Area of Science:

• Immunology
• Transplantation Medicine

Background:

• Belatacept treatment in kidney transplant recipients (KT) is linked to lower de novo donor-specific anti-HLA antibody (DSA) incidence.
• In vitro studies suggest a correlation between belatacept's half-maximal effective concentration (EC50) and therapeutic trough concentrations (C0).

Purpose of the Study:

• To investigate belatacept's inhibitory effect on B-cell alloantigen presentation and alloresponse.
• To determine if these effects occur at known therapeutic trough concentrations (C0).

Main Methods:

• Peripheral blood leukocytes (PBL) from healthy adults were cultured with HLA-mismatched PBL or alloantigenic lysate.
• Increasing concentrations of belatacept were added, and EC50 values were calculated.
• B-cell subsets and alloresponses were analyzed using flow cytometry.

Main Results:

• Belatacept significantly decreased alloreactive CD154+ B-cells and their subsets in a dose-dependent manner.
• Median EC50 values varied across B-cell subsets, with isotype-switched memory B-cells showing the highest resistance.
• Belatacept did not affect B-cell alloantigen presentation.

Conclusions:

• Belatacept demonstrates immunosuppressive activity against B-cell alloresponses at C0 levels below 10 µg/ml.
• This B-cell suppression mechanism contributes to the observed reduction in DSA formation in kidney transplant patients treated with belatacept.