Table 1

Natural IgA and specific IgA production in germ free mice monoassociated with individual bacteria^a

	Listeria monocytogenes actA(−)^a	Morganella morganii	Segmented filamentous bacterium	Oochrobactrum anthropi	Helicobacter muridarum
Mouse strain	GF C3H	GF C3H	GF C3H	GF BALB/c	GF BALB/c
Day after colonisation^1-b	21	28	14	54	14
Total IgA (ng/ml)^1-c	2200	924	2460	560	491
Specific IgA^1-d (ng/ml)	320	44	33	0	4
% Specific IgA	14.6	4.8	1.3	0	0.8

^a L monocytogenes actA (−) is a mutant strain of Listeria where the actA gene is inactive. The actA gene is important in translocation of Listeria across epithelial cells.M morganii is a gram positive commensal bacterium that can translocate into the host but has not been shown to be pathogenic.3 Segmented filamentous bacterium is a strictly anaerobic commensal bacterium which cannot be grown outside of the host.4 O anthropi is an aerobic gram negative bacterial strain which grows poorly in the intestinal tract and almost does not translocate into the host.31 H muridarum is a commensal bacterium which has been described to live in the crypts of the large intestine and has no history of pathogenic properties.
↵1-b Time of maximal specific antibody output after colonisation.
↵1-c IgA production was determined in Peyer's patches (PP) and small intestinal (SI) fragment cultures by radioimmunoassay. Typical values for output of total IgA from PP and SI fragment cultures are: 3000–4000 ng/ml for CNV mice and 100–200 ng/ml for GF mice.
↵1-d Specific IgA production was determined by radioimmunoassay on plates that were coated with lysates derived from the involved bacteria.