Identification in milk of a serum amyloid A peptide chemoattractant for B lymphoblasts.
BACKGROUND
Normal mammary gland contains an extravascular population of B lymphoblasts, precursors of the immunoglobulin plasma cells that play a key role in the passive protection of neonates by secreting immunoglobulins to colostrum and milk. We investigated the presence of chemoattractants in the milk by analysing the chemoattractant activity of various fractions of this secretion. Milk chemoattractants are potentially involved in the recruitment of lymphocytes from the maternal bloodstream in lactating mammary glands.


RESULTS
The dilution-related lymphoid cell chemoattraction of whey was associated with a < 10 kDa ultrafiltrate. Active fractions were purified by reverse-phase high performance liquid chromatography. Two peptides of 2.7 kDa (DMREANYKNSDKYFHARGNYDAA) and 1 kDa (RPPGLPDKY) were identified as fragments of the SAA protein family, tentatively identified as SAA2. Only the 2.7 kDa synthetic peptide displayed chemotactic activity, at two different optimal concentrations. At the lower concentration (3.7 nM), it attracted B-cell lymphoblasts, whereas at the higher (3.7 microM), it attracted B lymphocytes. Then, the SAA mRNA expression was analysed and we observed more SAA transcripts during lactation than gestation.


CONCLUSIONS
These data are consistent with the SAA23-45 fragment being involved in preplasma B-cell recruitment to the mammary gland and resultant benefit to the neonate.
de Jesus Rodriguez
Berardo
B
Institut National de la Recherche Agronomique, UR1282, Infectiologie Animale et Santé Publique, Nouzilly, Tours, France. birdo77@yahoo.com
Chevaleyre
Claire
C
Henry
Gwénaële
G
Mollé
Daniel
D
Virlogeux-Payant
Isabelle
I
Berri
Mustapha
M
Boulay
François
F
Léonil
Joëlle
J
Meurens
François
F
Salmon
Henri
H
D000595:Amino Acid Sequence; D000818:Animals; D016175:B-Lymphocyte Subsets / Q000166:cytology / Q000276:immunology / Q000378:metabolism*; D001402:B-Lymphocytes / Q000166:cytology / Q000276:immunology / Q000378:metabolism*; D002460:Cell Line; D002465:Cell Movement / Q000276:immunology; D005591:Chemical Fractionation; D005260:Female; D007774:Lactation / Q000276:immunology; D008321:Mammary Glands, Animal / Q000378:metabolism; D013058:Mass Spectrometry; D008892:Milk / Q000737:chemistry / Q000378:metabolism*; D008894:Milk Proteins / Q000276:immunology / Q000378:metabolism; D008969:Molecular Sequence Data; D010455:Peptides / Q000138:chemical synthesis / Q000276:immunology / Q000378:metabolism*; D000685:Serum Amyloid A Protein / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D013552:Swine; D013556:Swine, Miniature; D000067816:Whey Proteins
D008894:Milk Proteins; D010455:Peptides; D000685:Serum Amyloid A Protein; D000067816:Whey Proteins