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Abnormalities of serum-free light chain in patients with primary antibody deficiency in the absence of B lymphocyte clonality
  1. David Joseph Unsworth,
  2. Michael John Wallage,
  3. Esha Sarkar,
  4. Robert John Lock
  1. Department of Immunology and Immunogenetics, Pathology Sciences, North Bristol NHS Trust, Southmead Hospital, Bristol, UK
  1. Correspondence to Dr David Joseph Unsworth, Department of Immunology and Immunogenetics, Pathology Sciences, North Bristol NHS Trust, Southmead Hospital, Bristol BS10 5NB, UK; Joe.Unsworth{at}nbt.nhs.uk

Abstract

Aims A review of practice to determine whether serum-free light chain (SFLC) assays are helpful in detecting underlying clonal B-cell disorders or amyloidosis in patients with primary antibody deficiency (PAD) and recurrent infection.

Methods SFLC were assayed by nephelometry (BN2 nephelometer, Siemens; FREELITE assay, Binding Site). We reviewed SFLC test results recorded in our regional laboratory over a 4-year time period; 20 adults with PAD were identified as having been tested on at least two occasions.

Results Of 20 patients, 4 with PAD had abnormal serum-free kappa/lambda (K/L) ratios but no evidence of B-cell clonality. We also found extremely low levels of kappa and or lambda (below the limits of reliable detection) in 19/20 PAD cases (mostly common variable immunodeficiency), such that in many, ratios were not calculable.

Conclusions The data suggest that the abnormal ratios are generated by an inability to produce and/or secrete SFLCs, particularly kappa FLC. In this small initial study, we seek to highlight PAD cases where a suspicious K/L ratio, typically with very low absolute quantities of SFLCs, most likely points to B-cell dysfunction, rather than to B lymphocyte clonality.

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