Munc13-4 deficiency with CD5 downregulation on activated CD8+ T cells

Area of Science:

• Immunology
• Genetics
• Pediatrics

Background:

• Familial hemophagocytic lymphohistiocytosis (FHL) is a rare, life-threatening hyperinflammatory condition.
• FHL is characterized by uncontrolled T cell and macrophage activation, leading to cytokine storm.
• FHL subtypes are defined by genetic defects affecting cytotoxic lymphocyte function.

Observation:

• A previous study identified increased CD8(+) T cells with CD5 downregulation during active FHL type 2 (perforin deficiency).
• This T cell subset decreased after treatment, correlating with reduced cytokine levels.
• The presence of this subset in other FHL types remained uncharacterized.

Findings:

• This study reports a patient with FHL type 3 (Munc13-4 deficiency) due to UNC13D mutations.
• The patient exhibited elevated pro-inflammatory cytokines and a significant increase in activated CD8(+) T cells with CD5 downregulation during the acute phase.
• These immunophenotypic findings in FHL3 mirrored those previously observed in FHL2.

Implications:

• The CD8(+) T cell subset with CD5 downregulation may be a common biomarker for immune dysregulation across different FHL subtypes.
• This finding could aid in diagnosing and monitoring FHL3, potentially improving patient management.
• Further research is warranted to validate this immunophenotypic marker in a larger FHL cohort.