Table 2: Suggested immunological distinctions between SCID patients presenting with residual T lymphocytes of different origins.

Origin of patient’s cells Allo-reactive T cellsAuto-reactive T cellsResidual T cells

SCID phenotype Transplacentally acquired maternal lymphocytesOmenn MHC-II deficiency
Autoimmunity + +++
Eosinophilia +
Lymphocyte count Normal NormalNormal
Lymphocyte subset Inconsistent, based on the TCR clonalityInconsistent, based on the TCR clonality Usually CD4/CD8 reverse ratio
Immunoglobulin levelsLow Low Low
Lymphocytes response to mitogensLow Low Normal
TREC UD UD Normal
TCR-V repertoireSkewed, restricted Monoclonal Polyclonal
Treg cells High Inconsistent Normal

UD: undetectable, TCR: T cell receptor, TREC: TCR excision circles, Treg: regulatory T cells.