After monoassociation of Bifidobacterium
longum with germ-free BALB/c mice (nu/ +, heterozygous to nu gene), B. longum was recovered (l02-104
viable units per organ) from the mesenteric lymph
nodes, liver and kidneys for 2 weeks post intragastric
inoculation, but not after 4 weeks and later. Cessation
of bacterial translocation was not observed in
monoassociated nude (nu/nu) mice. Anti-B. longum
IgA antibody was detected by ELISA using B. longum
cell wall antigen in bile from Week 1 and in ileac wall
extract from Week 8 post-association in both nu/ +
and nu/nu mice. Total IgA levels in bile, ileac wall
extract and caecal contents were also elevated in both
mice after monoassociation. Cell-mediated immunity
measured by the footpad test and macrophage migration inhibition test using B. longum protein fraction
was detected in nu/ + mice in Week 4 and later, but not
in nu/nu mice. Nu/nu mice reconstituted 4 weeks prior
to monoassociation with lymphocytes from florabearing nu/ + mice developed delayed footpad reactivity and bacterial translocation stopped after 4 weeks.
Cell-mediated immunity rather than IgA antibody
correlated well with the cessation of translocation.