Table 2.

B lymphocyte compartment in subjects with Down syndrome

Author	Year	Number of subjects	Age	Main result
Cossarizza et al. [47]	1990	15 DS children	NA	Decrease of B lymphocytes absolute number and percentage
		16 age-matched controls
Cetiner et al. [63]	2010	32 DS subjects	DS subjects: mean age = 3.9 years	Lower percentages of B cells
		32 age-matched controls	Controls: mean age = 4.5 years
Verstegen et al. [71]	2010	95 DS subjects	Children. Mean age NA	Decrease in B lymphocyte counts. Lack of vast expansion of B cells within the first years of life. Decrease in transitional and naive B lymphocytes. Disturbed peripheral B lymphocyte maturation
		33 age-matched controls
Joshi et al. [48]	2011	12 DS subjects	DS subjects: mean age = 9.4 years	Decrease of B lymphocytes absolute number and percentage. Decreased total memory and class-switched memory B cells
		12 age-matched controls	Controls: mean age = 9.4 years
Trotta et al. [50]	2011	24 DS subjects	DS subjects: mean age = 38 years	Lower percentages of B lymphocytes
		21 age-matched controls	Controls: mean age = 43 years
Verstegen et al. [73]	2014	13 DS subjects	DS subjects: mean age = 11.3 years	In blood, decrease in B lymphocytes. Lower numbers of naïve mature B cells. Normal numbers of transitional B cells. Lower numbers of memory B cells
		43 age-matched controls	Controls: mean age = NA	In tonsils, normal germinal center cells
Carsetti et al. [72]	2015	26 DS subjects	DS subjects: median age = 8.74 years	Lower circulating B lymphocytes. Reduction in transitional and mature-naïve B cell numbers. Lower frequency of switched memory B cells specific for vaccine antigens
		26 age-matched controls	Controls: median age = 8 years
Valentini et al. [29]	2015	15 DS subjects	DS subjects: median age = 6.6 years	Reduction of total, mature, naïve, and transitional B cells. Severe reduction of switched memory B cells
		15 age-matched controls	Controls: median age = 7.8 years
Schoch et al. [49]	2017	40 DS subjects	DS subjects: mean age= 7.4 years	Lower percentage of B cells
		51 age-matched controls	Controls: mean age = 8.8 years
Farroni et al. [55]	2018	12 DS subjects	NA	In tonsils, similar frequency of total B cells. Increase in naïve B cells, with reduction in memory B cells
		11 age-matched controls		Impairment of the germinal center reaction
Waugh et al. [56]	2019	18 DS subjects	DS subjects: median age = 29.5 years	Depletion of immature naïve, pre-switched activated and memory B cells. Increase in terminally differentiated plasmablasts. Increase in B cells expressing CD11c (signature phenotype of age-associated B cells)
		18 age-matched controls	Controls: median age = 28.0 years

DS, Down syndrome; NA, not available