A composition which induces proliferation and/or accumulation of regulatory T cells, the composition comprising, as an active component, a combination of 5-17 of (a)-(q): (a) an isolated bacterial strain containing DNA comprising a nucleotide sequence that has at least 97%, 98% or 99% homology with SEQ ID NO: 19; (b) an isolated bacterial strain containing DNA comprising a nucleotide sequence that has at least 97%, 98% or 99% homology with SEQ ID NO: 20; (c) an isolated bacterial strain containing DNA comprising a nucleotide sequence that has at least 97%, 98% or 99% homology with SEQ ID NO: 21; (d) an isolated bacterial strain containing DNA comprising a nucleotide sequence that has at least 97%, 98% or 99% homology with SEQ ID NO: 22; (e) an isolated bacterial strain containing DNA comprising a nucleotide sequence that has at least 97%, 98% or 99% homology with SEQ ID NO: 24; (f) an isolated bacterial strain containing DNA comprising a nucleotide sequence that has at least 97%, 98% or 99% homology with SEQ ID NO: 25; (g) an isolated bacterial strain containing DNA comprising a nucleotide sequence that has at least 97%, 98% or 99% homology with SEQ ID NO: 26; (h) an isolated bacterial strain containing DNA comprising a nucleotide sequence that has at least 97%, 98% or 99% homology with SEQ ID NO: 27; (i) an isolated bacterial strain containing DNA comprising a nucleotide sequence that has at least 97%, 98% or 99% homology with SEQ ID NO: 30; (j) an isolated bacterial strain containing DNA comprising a nucleotide sequence that has at least 97%, 98% or 99% homology with SEQ ID NO: 31; (k) an isolated bacterial strain containing DNA comprising a nucleotide sequence that has at least 97%, 98% or 99% homology with SEQ ID NO: 32; (l) an isolated bacterial strain containing DNA comprising a nucleotide sequence that has at least 97%, 98% or 99% homology with SEQ ID NO: 33; (m) an isolated bacterial strain containing DNA comprising a nucleotide sequence that has at least 97%, 98% or 99% homology with SEQ ID NO: 34; (n) an isolated bacterial strain containing DNA comprising a nucleotide sequence that has at least 97%, 98% or 99% homology with SEQ ID NO: 39; (o) an isolated bacterial strain containing DNA comprising a nucleotide sequence that has at least 97%, 98% or 99% homology with SEQ ID NO: 40; (p) an isolated bacterial strain containing DNA comprising a nucleotide sequence that has at least 97%, 98% or 99% homology with SEQ ID NO: 41; and (q) an isolated bacterial strain containing DNA comprising a nucleotide sequence that has at least 97%, 98% or 99% homology with SEQ ID NO: 42. (a) an isolated bacterial strain containing DNA comprising a nucleotide sequence that has at least 97%, 98% or 99% homology with SEQ ID NO: 19; (b) an isolated bacterial strain containing DNA comprising a nucleotide sequence that has at least 97%, 98% or 99% homology with SEQ ID NO: 20; (c) an isolated bacterial strain containing DNA comprising a nucleotide sequence that has at least 97%, 98% or 99% homology with SEQ ID NO: 21; (d) an isolated bacterial strain containing DNA comprising a nucleotide sequence that has at least 97%, 98% or 99% homology with SEQ ID NO: 22; (e) an isolated bacterial strain containing DNA comprising a nucleotide sequence that has at least 97%, 98% or 99% homology with SEQ ID NO: 24; (f) an isolated bacterial strain containing DNA comprising a nucleotide sequence that has at least 97%, 98% or 99% homology with SEQ ID NO: 25; (g) an isolated bacterial strain containing DNA comprising a nucleotide sequence that has at least 97%, 98% or 99% homology with SEQ ID NO: 26; (h) an isolated bacterial strain containing DNA comprising a nucleotide sequence that has at least 97%, 98% or 99% homology with SEQ ID NO: 27; (i) an isolated bacterial strain containing DNA comprising a nucleotide sequence that has at least 97%, 98% or 99% homology with SEQ ID NO: 30; (j) an isolated bacterial strain containing DNA comprising a nucleotide sequence that has at least 97%, 98% or 99% homology with SEQ ID NO: 31; (k) an isolated bacterial strain containing DNA comprising a nucleotide sequence that has at least 97%, 98% or 99% homology with SEQ ID NO: 32; (l) an isolated bacterial strain containing DNA comprising a nucleotide sequence that has at least 97%, 98% or 99% homology with SEQ ID NO: 33; (m) an isolated bacterial strain containing DNA comprising a nucleotide sequence that has at least 97%, 98% or 99% homology with SEQ ID NO: 34; (n) an isolated bacterial strain containing DNA comprising a nucleotide sequence that has at least 97%, 98% or 99% homology with SEQ ID NO: 39; (o) an isolated bacterial strain containing DNA comprising a nucleotide sequence that has at least 97%, 98% or 99% homology with SEQ ID NO: 40; (p) an isolated bacterial strain containing DNA comprising a nucleotide sequence that has at least 97%, 98% or 99% homology with SEQ ID NO: 41; and (q) an isolated bacterial strain containing DNA comprising a nucleotide sequence that has at least 97%, 98% or 99% homology with SEQ ID NO: 42.