B. Kulseng et al., Transplantation of alginate microcapsules - Generation of antibodies against alginates and encapsulated porcine islet-like cell clusters, TRANSPLANT, 67(7), 1999, pp. 978-984
Background. Microencapsulation of islets of Langherhans in alginate poly-l-
lysine capsules provides an effective protection against cell-mediated immu
ne destruction, and ideally should allow the transplantation of islets in t
he absence of immunosuppression. It has previously been suggested that algi
nate rich in mannuronic acid (high M) is more immunogenic than alginate ric
h in guluronic acid (high G). The ability of these alginates to induce an a
ntibody response in the recipient or act as an adjuvant to antibody respons
es against antigens leaked from the capsule was investigated in the present
study.
Methods. Empty capsules made from these different types of alginate were tr
ansplanted intraperitoneally to Wister rats or Balb/c mice. In addition, so
me animals were also injected with bovine serum albumin to assess the abili
ty of the alginates to act as an adjuvant to this antigen, Antibody respons
es to intraperitoneally transplanted free and microencapsulated fetal porci
ne islet like cell clusters (ICC) were also evaluated, in animals treated w
ith or without cyclosporine.
Results. Antibodies against high M-alginate capsules were detected in the s
era of mice transplanted with this capsule type. However, this response was
not seen after the transplantation of high G capsules. When Wister rats we
re used as recipients, no antibody responses were detected against any type
of alginate capsules. Neither type of capsule acted as an adjuvant. Antibo
dies against ICC were present, in rats transplanted with both nonencapsulat
ed and encapsulated ICCs, Administration of cyclosporine could abolish this
production of antibodies against ICC,
Conclusions. High G-alginate capsules are less immunogenic than high M caps
ules. Because encapsulation did not protect against the generation of antib
odies against ICC, it can be assumed that antigen leakage from the capsules
occurs, as no evidence was found for capsules breaking in vivo.