The following is a summary of “Normal B-cell ranges in infants: A systematic review and meta-analysis,” published in the November 2022 issue of Allergy and Clinical Immunology by Borriello, et al.

B-cell levels are a useful gauge of whether environmental influences, such as exposure to B-cell-depleting medications, have a negative effect on immune system development during the first year of life. B-cell levels in healthy newborns by age do not, however, fall within any established reference limits. By combining data from previous research, researchers sought to determine the typical range of B-cell counts in babies, by age, during the first year of life.

Through a thorough literature review, studies reporting B-cell counts assessed by flow cytometry and CD19 markers in healthy newborns were found. Through age group and/or continuous age, quality and feasibility evaluations evaluated appropriateness for inclusion in meta-analyses was evaluated by quality and feasibility evaluations. Absolute and percentage B-cell numbers were assessed as means and normal ranges (2.5th-97.5th percentile). The effects of different assumptions were evaluated using sensitivity studies.

In at least one meta-analysis, 28 of the 37 relevant papers were found. The average and typical B-cell concentrations were found to be 707 cells/μL in cord blood (range: 123–2,324 cells/μL), 508 cells/μL in infants aged 0–1 month (range: 132–1,369 cells/μL), 1,493 cells/μL in infants aged 1–6 months (range 416-, cells/μL), and 1,474 cells/μL in infants older than 6 months (range 416-3,805 cells/μL). B-cell levels reached their peak at week 26, according to the continuous age model. Both the percentage B-cell estimations and the results of the sensitivity studies showed similar trends.

By the week of age, during the first year of life, these meta-analyses offer the first normal reference ranges for B-cell numbers in babies.