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Trophozoites of Giardia ardeae were obtained from the great blue heron (Ardea herodias) and established in axenic culture using the TYI-S-33 medium. The generation time in culture for G. ardeae was 22-25 hr, which was 3-fold longer than for Giardia duodenalis (WB strain). A morphological comparison of trophozoites in the original intestinal isolate to those grown in culture revealed that they were identical for the following characteristics: a pyriform-shaped body, a ventral adhesive disc with a deep notch in the posterior border, teardrop-shaped nuclei, pleomorphism in median body structure ranging from a round-oval appearance (Giardia muris type) to that of a clawhammer (G. duodenalis type), and a single caudal flagellum on the right side (as viewed dorsally) with the left one being rudimentary. Analysis of the chromosomal migration patterns was performed by orthogonal-field-alternation gel electrophoresis and demonstrated that the pattern for G. ardeae was distinctly different from that for G. duodenalis (Portland 1-CCW strain). Bacterial symbionts were seen attached to trophozoites in the original isolate but could not be detected in cultured trophozoites using scanning electron microscopy, fluorescence light microscopy using the Hoechst 33258 dye for DNA localization, or by standard microbiological techniques using nonselective media for growing aerobic or anaerobic bacteria. This study demonstrated that avian-derived Giardia could be grown in axenic culture; based on morphological criteria and chromosomal migration patterns, that G. ardeae should be considered a distinct species; and that rationale for determining Giardia spp., based on median body structure alone, should no longer be considered adequate for classification at the species level.

Numerous membrane-bounded vacuoles are found adjacent to the plasma membrane of the pathogenic protozoan Giardia lamblia. The function of these vacuoles has been discussed by several authors. Approximately 100-400 nm in diameter with a core of low electron density, they have been suggested to be mitochondria, mucocysts, lysosomes, and endocytotic vacuoles. Enzyme cytochemical localization for acid phosphatase activity using cerium as a capturing agent demonstrates reaction product in these vacuoles as well as in the endoplasmic reticulum and nuclear envelope cisternae. The distribution of reaction product suggests the vacuoles are lysosome-like; however, their function and development remain in question.

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A double labeling technique was developed to detect T cell phenotype and HLA‐DR (activation) antigens on infiltrating cells in gingival biopsy sites classified as either periodontally active (≥ mm attachment loss within past 3 months), clinically similar but stable, or healthy. Serial cryostat sections were obtained from each of the above disease category biopsies in 13 periodontal maintenance patients, and were processed with sequential Leu series (T cell subsets) avidinbiotin‐peroxidase followed by anti‐HLA‐DR indirect alkaline phosphatase labeling protocols. Labeled cells were counted in repeatable fields in the sulcular, middle and oral thirds of each section, and HLA‐DR+ T cells (activated) were calculated. Total HLA‐DR‐labeled cells and HLA‐DR‐positive pan‐T cells and T helper cells (Th) were all more numerous in active specimens than in healthy sites (p<0.05), and in sulcular fields than in the oral third of the section (p<0.05). Although activated T suppressor cell (T5) densities did not vary statistically according to tissue location, active biopsies had more cells per field than either stable or healthy specimens (p<0.05), especially in the sulcular third. A majority of pan‐T, Ts and Th cells appeared to display activation markers in active, stable and healthy biopsies. This study supports the functional role of T lymphocytes in modulating the immune response in periodontal tissues.