The microencapsulation of cells within alginate poly-L-lysine microcapsules prepared with the standard single step drop technique: histologically identified membrane imperfections and the associated graft rejection.

Standard alginate-polylysine microcapsules containing isolated rat hepatocytes were prepared. These capsules were intraperitoneally implanted into mice, and retrieved after seven days. Histological sections of the recovered microcapsules showed peritoneal lymphocyte and macrophage infiltration. Additional microscopic observations at various stages of the microencapsulation procedure, and histological observations of control non-implanted microcapsules; illustrate that encapsulated cells became embedded within the microcapsular membrane matrix. The microcapsular membrane at these sites appeared thin and often poorly formed. The cellular infiltration into the implanted microcapsules can occur through holes developed in these thin and poorly formed areas found in the microcapsular membrane. Similar observations were seen in microcapsules prepared with 20 x 10(6) and at a lower cell concentration of 10 x 10(6) suspended cells per millilitre of sodium alginate.