Morphological and immunologic aspects of the cecal appendix of the rabbit

Abstract

FOR MANY YEARS, THE RABBIT HAS BEEN USED AS A LABORATORY ANIMAL; HOWEVER, UP UNTIL NOW, LITTLE IS KNOWN ABOUT THE PRECISE FUNCTION OF SOME OF HIS ORGANS, LIKE THE CECAL APPENDIX. THE OBJECTIVE OF THE PRESENT STUDY WAS TO DESCRIBE SOME ASPECTS RELATED TO THE LYMPHOCYTE COMPOSITION, IN ORDER TO UNDERSTAND SOME IMMUNOLOGIC ANSWERS OF THE ORGAN IN ANIMAL MODELS. AN ANATOMICAL, HISTOLOGICAL AND IMMUNOHISTOLOGICAL STUDY OF THE CECAL APPENDIX WAS CARRIED OUT ON NEW ZEALAND RABBIT FROM ITS FETUS STAGE UNTIL THREE YEARS OLD, BY CONVENTIONAL TECHNIQUES OF DISSECTION, MICROSCOPY WITH PARAFFIN CUTS STAINED WITH HEMATOXILIN AND EOSIN, AS WELL AS IMMUNOPEROXIDASE TECHNIQUES, FOR MARKERS OF LYMPHOCYTES"" DIFFERENTIATION CD4, CD43, CD25 AND CD5; AS WELL AS HISTOCHEMICAL TECHNIQUES TO LOOK FOR PLASMATIC CELLS, IN THIS WAY, THE MARKED LYMPHOCYTES WERE COUNTED BY OPTIC MICROSCOPY COUPLED TO AN ANALYSER OF IMAGES. CHANGES IN THE MUCOSAL AND THE SUBMUCOSAL LAYERS WERE OBSERVED WITH TWO TYPES OF PROJECTIONS, VILLUS AND DOME, WITH EPITHELIUM THAT SUGGESTS AN ABSORPTION/SECRETION FUNCTION IN THE VILLI AND ANTIGEN EXCHANGE IN THE DOME. THE LYMPHOCYTES POPULATION WAS BIGGER AND MORE DEFINED IN THE DOME (P < 0.05) AND IT IS CONSTITUTED BY TWO LYMPHOID NODULES, THE SUPERFICIAL ONES IN THE MUCOUS LAYERS WITH PREDOMINANCE OF T ACTIVE AND RESPONSIVE LYMPHOCYTES, MARKED WITH CD43, IN COMPARISON TO THE DEEPEST ONES IN THE SUBMUCOSAL LAYERS WITH CD4 LYMPHOCYTES AND PLASMATIC CELLS (P < 0.05). THE FULL STRUCTURAL APPENDIX DEVELOPMENT IS ACQUIRED FROM 30 DAYS OF AGE, IN ANIMALS OF 60 DAYS, THE NODULE OF THE MUCOUS LAYER HAS CHARACTERISTICS OF SECONDARY LYMPHOID AREA, RESEMBLING JEJUNAL PEYER'S PATCHES; WHILE THE DEEP ONE MAINTAINS CHARACTERISTICS OF PRIMARY LYMPHOID AREA , RESEMBLING THE FABRICIUS BURSA, DEVELOPING SINCE BIRTH AND PERSISTING A LIFETIME.