Coelomocytes as Effector Cells in Eartworm Immunity

Abstract

The results from this study support the following hypothetical mechanism for the rejection of xenografts by Lumbricus. Initially, coelomocytes are attracted to xenografts due to the stimulus of tissue injury. This results in clumping or nodule formation around injured and loose muscle fibers, and a general clumping of baso-phils. Clumping may entran acidophilic cells and/or attract such cells to the graft site. Because the graft is a foreign tissue, its foreignness also stimulates a cellular response. Basophils invade the muscular structure of the xenograft and more acidophilic cells accumulate at the graft site. The acidophilic cells have the canacity to digest the connective tissue elements which hold the muscle fibers of the graft in place. Dissolution of these connective tissue elements results in the release of muscle fibers. The presence of free foreign muscular tissue in the coelomic cavity acts as a stimulus for further accumulations of basophilic cells, which in turn form more capsules and may attract more acidophils. Thus there is a continuous erosion of xenograft muscle by acidophils and a clearing away of debris by basophils. This process eventually leads to the complete destruction of a xenograft.

Autografts stimulate the accumulation of basophils due to the presence of injured tissue. The presence of cell clumps and/or injured tissue also causes acidophilic cells to accumulate under the graft. Only injured or dead tissue is acted upon by the coelomic cells since the stimulation of any further cellular invasion into the graft by a foreign antigen, is not present in autografts. Acidophilic coelomic cells, either do not release substances that can attack the connective tissues of autografts, or the substances released by these cells does not react with non-injured self tissue. This mechanism together with other information concerning specificity and anamnesis in the rejection response of the annelid Lumbricus terrestris, offers further support for a true immunologi-cal response to tissue grafts in an invertebrate.