Abstract: The present invention is to provide a cellulose acetate that has a low total degree of acetyl substitution and a degree of acetyl substitution at 6-position that is lower compared to the degrees of acetyl substitution at 2-position and 3-position of a glucose ring, and has excellent water solubility. A cellulose acetate having: a total degree of acetyl substitution of 0.4 or greater and 0.9 or less, a proportion of a degree of acetyl substitution at 6-position in the total degree of acetyl substitution of 0% or greater and 18% or less, and a light transmittance at 660 nm of 5% or greater in 4 wt. % aqueous solution.

Abstract: An object is to provide a Th1-increasing agent that can reduce constraints on storage conditions and feeding form and sufficiently increase Th1 at lower doses. A Th1-increasing agent containing a cellulose derivative as an active ingredient, the cellulose derivative having a degree of butyryl substitution of 0.3 or greater and 2.6 or less, and a total degree of substitution of 0.5 or greater and 2.8 or less.