A proposed algorithm predictive for cytotoxic T cell alloreactivity.

Area of Science:

• Immunology
• Transplantation Immunology
• Computational Biology

Background:

• Previous research indicated a decrease in T cell alloreactivity with more amino acid differences in HLA class I mismatches.
• The impact of individual amino acid differences on T cell alloreactivity was not fully understood, prompting investigation into positional and physicochemical effects.

Purpose of the Study:

• To investigate the influence of specific amino acid positions and physicochemical properties on T cell alloreactivity in single HLA class I mismatches.
• To develop a predictive algorithm for T cell alloreactivity in hematopoietic stem cell transplantation donor selection.

Main Methods:

• Analysis of 131 patient/donor pairs with single HLA-A or -C mismatches, compatible for HLA-B, -DRB1, and -DQB1.
• Determination of alloreactive cytotoxic T lymphocyte precursor (CTLp) frequency and association with amino acid differences in HLA class I mismatches.
• Bivariate and multivariate analyses to identify critical amino acid positions and properties influencing CTLp outcome.

Main Results:

• Amino acid differences in alpha helices affected CTLp outcome regardless of physicochemical compatibility, while beta sheet differences only impacted it if physicochemical properties were incompatible.
• Specific positions (62, 63, 73, 80, 116, 138, 144, 163) were highly predictive of negative CTLp outcomes.
• A weighted predictive mismatch score was developed, estimating up to a 13-fold increased likelihood of negative CTLp in high-scoring pairs.

Conclusions:

• The position and physicochemical properties of amino acid differences are crucial determinants of T cell alloreactivity in HLA class I mismatches.
• The developed weighted mismatch score algorithm shows promise as a tool for optimizing donor selection in hematopoietic stem cell transplantation.
• This approach may improve transplant outcomes by better predicting and mitigating T cell-mediated rejection.