Memory B-cell phenotyping in cvid – a journey through buddha’s nostril?

Common variable immunodeficiency (CVID) is a heterogeneous B-cell immunodeficiency disorder often characterised by failure of memory B-cell development and antibody secretion. Attempts have been made to stratify patients into clinical subsets based on aberrations in B-cell development very frequently found in this condition, the most characteristic subset being the ‘inflammatory’ group (‘Freiburg Ia’) characterised by a relative lack of memory B cells, and an expansion of CD21 negative B cells. Cohorts of CVID patients have been studied, largely in Europe, and cut-offs for the critical parameters established, along with their clinical implications. However, such cut-offs are only generalisable if similar values can be obtained across various laboratories. To assess this, we undertook a quality assurance program (QAP) in up to six laboratories in Australia, involving 16 specimens. We found marked variability in critical B-cell parameters, and an evident lack of consensus in classification allocation. Some of this variability could be explained by variations in cell preparation method, gating strategy, and cytometer platform, whilst some were difficult to explain. Thus, progress in B-cell phenotyping in CVID is likely to require strict standardisation of methodology, reagent, cytometer, and gating, and (since such parameters were unlikely to reflect the original European studies) a revision of normal ranges based on such standardised methodology. Common variable immunodeficiency (CVID) is a heterogeneous B-cell immunodeficiency disorder often characterised by failure of memory B-cell development and antibody secretion. Attempts have been made to stratify patients into clinical subsets based on aberrations in B-cell development very frequently found in this condition, the most characteristic subset being the ‘inflammatory’ group (‘Freiburg Ia’) characterised by a relative lack of memory B cells, and an expansion of CD21 negative B cells. Cohorts of CVID patients have been studied, largely in Europe, and cut-offs for the critical parameters established, along with their clinical implications. However, such cut-offs are only generalisable if similar values can be obtained across various laboratories. To assess this, we undertook a quality assurance program (QAP) in up to six laboratories in Australia, involving 16 specimens. We found marked variability in critical B-cell parameters, and an evident lack of consensus in classification allocation. Some of this variability could be explained by variations in cell preparation method, gating strategy, and cytometer platform, whilst some were difficult to explain. Thus, progress in B-cell phenotyping in CVID is likely to require strict standardisation of methodology, reagent, cytometer, and gating, and (since such parameters were unlikely to reflect the original European studies) a revision of normal ranges based on such standardised methodology.