The early microbiota species composition may influence the B cell development in children

We never walk alone; each of us is colonized by scores of bacterial species that live in our gastrointestinal tract. The colonization event occurs right after birth and has profound effects on our immune system – this sentence appears in every modern immunology textbook. There is, however, no such thing like one human microbiome as the species composition in our gut depends on many aspects. Diet, geographical region we live in or civilization level of society we belong to may influence to what species we are exposed and most probably dictate also many qualitative features of human immune responses. But we do know yet many technical details of the interactions between the human microbiome species arrangement and our immune system characteristics. I have found the publication that studies what impact on the development of B cell populations in the childhood may have the early microbiota species composition in the gut.

The link: http://www.jimmunol.org/content/188/9/4315.abstract

The work is performed on Swedish children and it contains two parts. In the first authors follow the development of B cells in the analyzed cohort of individuals along the period that ranges from right after birth to three years of age. B cells from peripheral blood (defined as CD20+ cells from the lymphocyte gate) are subdivided into CD5+ population (secreting mostly polyreactive IgM antibodies) and CD27+ subset (whose majority are class-switched memory cells). The first population forms the bulk of B cells in children, it expand soon after birth and gradually contracts to reach low level in adults. The second subset grows much slower; it attains its plateau at 18 months of life and continues at similar numbers at 36 months (although there is still much more CD5+ B cells than CD27+ B cells at that time). In the adult blood CD27+ population prevails over CD5+ B cells.

For the second part authors collect fecal samples in the same cohort of children during the early weeks of their life (1, 2, 4 and 8) and study the microbiota species composition in obtained samples. To detect bacterial groups present in the analyzed material they use combined microbiological (growth conditions), biochemical and molecular approaches that identify Escherichia coliEnterobacteria that are not E.coliStaphylococcus aureusBacterioidesEnterococci, BifidobacteriaLactobacilli and Clostridia. Next investigators attempt to correlate quantitative features of B cell development (counts of CD20+, CD5+ and CD27+ cells) along the infancy period with qualitative aspects of microbiota composition (presence or absence of given bacterial groups) during the early weeks of life. The major conclusion of this paper is that the early presence of species or bacterial groups like E.coli and Bifidobacteria in children guts associates with the increased numbers of CD27+ B cells at 4 and 18 months of their life. However, the colonization with S.aureus correlates inversely with CD27+ B cell counts at 4 month.

Obviously correlations do not necessarily indicate for the casual bond but I think the data presented in this report are interesting especially when you combine them with the information that authors provide in the discussion part. According to that E.coli and Bifidobacteria are thought to be classical infantile bacterial species but S.aureus is not. This organism is considered to be a skin bacterium; however, it colonizes the gastrointestinal tract of Swedish children with high penetration (~70%) and may slow down the development of effective immune responses. Such publications are important because the incremental appreciation of how microbiota species composition regulates human immunity may let us use this knowledge for practical purposes in the future.

Lundell AC, Björnsson V, Ljung A, Ceder M, Johansen S, Lindhagen G, Törnhage CJ, Adlerberth I, Wold AE, & Rudin A (2012). Infant B cell memory differentiation and early gut bacterial colonization. Journal of immunology (Baltimore, Md. : 1950), 188 (9), 4315-22 PMID: 22490441

Advertisements
Leave a comment

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: