Comparison of NK-cell (Leu-7+ and Leu-11b+) populations in clinically healthy gingiva, chronic gingivitis and chronic adult periodontitis

Immunopathogenesis and immunotherapy of diabetes-associated periodontitis

OBJECTIVES

This paper aims to review the immunopathogenesis of Diabetes-associated periodontitis (DPD) and to propose a description of the research progress of drugs with potential clinical value from an immunotherapeutic perspective.

MATERIALS AND METHODS

A comprehensive literature search was conducted in PubMed, MEDLINE, Embase, Web of Science, Scopus and the Cochrane Library. Inclusion criteria were studies on the association between diabetes and periodontitis using the Boolean operator "AND" for association between diabetes and periodontitis, with no time or language restrictions. Search terms included diabetes mellitus, periodontitis, immunopathogenesis, specific immunity, non-specific immunity, flora, estrogen, pharmacological treatment, immunotherapy.

RESULTS

Alterations in the subgingival flora environment in a hyperglycemic environment elicit an immune response. Overactivity/suppression of nonspecific immune cells and impaired cellular defenses trigger specific immune responses. Epigenetics as well as female hormones also play a role. There is already a small amount of clinical evidence for the role of metronidazole, subantimicrobial doses of doxycycline, minocycline hydrochloride, and metformin in the treatment of DPD. Some preclinical studies have also accumulated experimental evidence for the improved effects of vitamin D3 and other drugs on DPD.

CONCLUSIONS

The development of diabetic periodontitis is immunologically linked to a state of immune imbalance and therefore holds great promise for the use of immunotherapeutic drugs.

CLINICAL SIGNIFICANCE

Immunotherapy with drugs along with periodontal nonsurgical treatment could provide ideas for DPD treatment based on the immunopathogenesis of DPD.

Predicting Key Genes and Therapeutic Molecular Modelling to Explain the Association between Porphyromonas gingivalis (P. gingivalis) and Alzheimer’s Disease (AD)

The association between Porphyromonas gingivalis (P. gingivalis) and Alzheimer’s disease (AD) remains unclear. The major aim of this study was to elucidate the role of genes and molecular targets in P. gingivalis-associated AD. Two Gene Expression Omnibus (GEO) datasets, GSE5281 for AD (n = 84 Alzheimer’s, n = 74 control) and GSE9723 (n = 4 P. gingivalis, n = 4 control), were downloaded from the GEO database. Differentially expressed genes (DEGs) were obtained, and genes common to both diseases were drawn. Additionally, Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) analysis was performed from the top 100 genes (50 upregulated and 50 downregulated genes). We then proceeded with CMap analysis to screen for possible small drug molecules targeting these genes. Subsequently, we performed molecular dynamics simulations. A total of 10 common genes (CALD1, HES1, ID3, PLK2, PPP2R2D, RASGRF1, SUN1, VPS33B, WTH3DI/RAB6A, and ZFP36L1) were identified with a p-value < 0.05. The PPI network of the top 100 genes showed UCHL1, SST, CHGB, CALY, and INA to be common in the MCC, DMNC, and MNC domains. Out of the 10 common genes identified, only 1 was mapped in CMap. We found three candidate small drug molecules to be a fit for PLK2, namely PubChem ID: 24971422, 11364421, and 49792852. We then performed molecular docking of PLK2 with PubChem ID: 24971422, 11364421, and 49792852. The best target, 11364421, was used to conduct the molecular dynamics simulations. The results of this study unravel novel genes to P. gingivalis-associated AD that warrant further validation.

Influence of Natural Killer Cells and Natural Killer T Cells on Periodontal Disease: A Systematic Review of the Current Literature

Natural killer (NK) cells, as members of the innate immune system, and natural killer T (NKT) cells, bridging innate and adaptive immunity, play a prominent role in chronic inflammatory diseases and cancerogenesis, yet have scarcely been examined in oral diseases. Therefore, systematic research on the latest literature focusing on NK/NKT cell-mediated mechanisms in periodontal disease, including the time period 1988-2020, was carried out in MEDLINE (PubMed) using a predetermined search strategy, with a final selection of 25 studies. The results showed that NK cells tend to have rather proinflammatory influences via cytokine production, cytotoxic effects, dendritic-cell-crosstalk, and autoimmune reactions, while contrarily, NKT cell-mediated mechanisms were proinflammatory and immunoregulatory, ranging from protective effects via B-cell-regulation, specific antibody production, and the suppression of autoimmunity to destructive effects via cytokine production, dendritic-cell-crosstalk, and T-/B-cell interactions. Since NK cells seem to have a proinflammatory role in periodontitis, further research should focus on the proinflammatory and immunoregulatory properties of NKT cells in order to create, in addition to antibacterial strategies in dental inflammatory disease, novel anti-inflammatory therapeutic approaches modulating host immunity towards dental health.

Bifidobacterium animalis subsp lactis HN019 presents antimicrobial potential against periodontopathogens and modulates the immunological response of oral mucosa in periodontitis patients

Objective

To evaluate the effects of Bifidobacterium animalis subsp. lactis HN019 (HN019) on clinical periodontal parameters (plaque accumulation and gingival bleeding), on immunocompetence of gingival tissues [expression of beta-defensin (BD)-3, toll-like receptor 4 (TLR4), cluster of differentiation(CD)-57 and CD-4], and on immunological properties of saliva (IgA levels) in non-surgical periodontal therapy in generalized chronic periodontitis (GCP) patients. Adhesion to buccal epithelial cells (BEC) and the antimicrobial properties of HN019 were also investigated.

Materials and methods

Thirty patients were recruited and monitored clinically at baseline (before scaling and root planing—SRP) and after 30 and 90 days. Patients were randomly assigned to Test (SRP+Probiotic, n = 15) or Control (SRP+Placebo, n = 15) group. Probiotic lozenges were used for 30 days. Gingival tissues and saliva were immunologically analyzed. The adhesion of HN019 with or without Porphyromonas gingivalis in BEC and its antimicrobial properties were investigated in in vitro assays. Data were statistically analyzed (p<0.05).

Results

Test group presented lower plaque index (30 days) and lower marginal gingival bleeding (90 days) when compared with Control group. Higher BD-3, TLR4 and CD-4 expressions were observed in gingival tissues in Test group than in Control group. HN019 reduced the adhesion of P. gingivalis to BEC and showed antimicrobial potential against periodontopathogens.

Conclusion

Immunological and antimicrobial properties of B. lactis HN019 make it a potential probiotic to be used in non-surgical periodontal therapy of patients with GCP.

Clinical relevance

B. lactis HN019 may be a potential probiotic to improve the effects of non-surgical periodontal therapy.

Name of the registry and registration number (ClinicalTrials.gov): “Effects of probiotic therapy in the treatment of periodontitis”—NCT03408548.

Comparison of peri-implant soft tissues in submerged versus transmucosal healing: A split mouth prospective immunohistochemical study

OBJECTIVE

The present split-mouth prospective study involves an immunohistochemical evaluation of peri-implant soft tissue healing after the osseointegration period, comparing submerged and transmucosal approaches using two-piece implant systems. The null hypothesis was that both surgical procedures elicit a similar immune response of the peri-implant soft tissues.

DESIGN

Thirty-one healthy patients were included in this study, in which two implants were placed in the right and left maxillary pre-molar regions. A total of 62 dental implants were analyzed, establishing a control side with 31 submerged implants, and a study side with 31 exposed implants bearing healing abutments. After a three-month healing period, a soft tissue biopsy was collected and prepared for immunohistochemical analysis of the proportions of different lymphocyte subpopulations.

RESULTS

The comparative analysis between the submerged and transmucosal approaches failed to identify statistically significant differences in CD19+ B cells, CD4+ T cells, CD8+ T cells, CD25+ T cells or γd T cells. However, significant differences in NK lymphocytes (p = 0.012) were recorded with the submerged surgical procedure.

CONCLUSIONS

Peri-implant soft tissue immune response with submerged or transmucosal healing protocols demonstrated comparable outcomes after the osseointegration period. There is sufficient evidence that the null hypothesis of no difference cannot be rejected. To the best of our knowledge, this is the first study of its kind. Further research is therefore needed to further clarify the role of these lymphocyte subpopulations in peri-implant soft tissues.

The influence of KIR gene presence/absence polymorphisms on the development of periodontal disease in smokers and non-smokers

Introduction

Periodontal diseases are highly prevalent inflammatory, multifactorial diseases. Smoking is one of the most important environmental risk factors for the development and severity of periodontal disease. Killer cell immunoglobulin-like receptors (KIRs) are members of the immunoglobulin (Ig) superfamily and play an essential role in the regulation of NK cell activity, allowing natural killer (NK) cells to sense and respond to human leukocyte antigen (HLA) class I. The aim of this study was to evaluate the influence of KIR gene presence/absence polymorphisms on the development of periodontal disease in smokers and non-smokers.

Material and methods

This study enrolled 400 Caucasian subjects (age range 25-69 years) from the West Pomeranian region of Poland. The subjects were categorized into four subgroups (smoking and non-smoking patients with periodontal disease; smoking and non-smoking subjects without periodontal disease - control subjects).

Results

The differences of KIR gene frequencies between non-smoking patients and non-smoking control subjects as well as smoking patients and control subjects were not statistically significant. In multivariate regression analysis advanced age of patients and smoking were independent factors associated with increased frequency of periodontal disease.

Conclusions

The results of this study suggest that the main factor associated with increased risk of periodontal disease is smoking, whereas KIR presence/absence polymorphism is not a significant factor involved in the pathogenesis of periodontal disease.

Natural Killer Cells in the Orchestration of Chronic Inflammatory Diseases

Inflammation, altered immune cell phenotype, and functions are key features shared by diverse chronic diseases, including cardiovascular, neurodegenerative diseases, diabetes, metabolic syndrome, and cancer. Natural killer cells are innate lymphoid cells primarily involved in the immune system response to non-self-components but their plasticity is largely influenced by the pathological microenvironment. Altered NK phenotype and function have been reported in several pathological conditions, basically related to impaired or enhanced toxicity. Here we reviewed and discussed the role of NKs in selected, different, and “distant” chronic diseases, cancer, diabetes, periodontitis, and atherosclerosis, placing NK cells as crucial orchestrator of these pathologic conditions.

Cellular composition of long-standing gingivitis and periodontitis lesions

BACKGROUND AND OBJECTIVE

Insufficient information on the cellular composition of long-standing gingivitis lesions without signs of attachment loss makes an understanding of differences in cellular composition between "destructive" and "nondestructive" periodontal lesions difficult. The aim of the current study was to analyze differences in cell characteristics between lesions representing long-standing gingivitis and severe periodontitis.

MATERIAL AND METHODS

Two groups of patients were recruited. One group consisted of 36 patients, 33-67 years of age, with severe generalized periodontitis (periodontitis group). The second group consisted of 28 patients, 41-70 years of age, with overt signs of gingival inflammation but no attachment loss (gingivitis group). From each patient a gingival biopsy was obtained from one selected diseased site and prepared for immunohistochemical analysis.

RESULTS

Periodontitis lesions were twice as large and contained significantly larger proportions, numbers and densities of cells positive for CD138 (plasma cells) and CD68 (macrophages) than did gingivitis lesions. The proportion of B cells that expressed the additional CD5 marker (B-1a cells) was significantly larger in periodontitis lesions than in gingivitis lesions. The densities of T cells and B cells did not differ between periodontitis lesions and gingivitis lesions. T cells were not the dominating cell type in gingivitis lesions, as B cells together with their subset plasma cells comprised a larger number and proportion than T cells.

CONCLUSION

Periodontitis lesions at teeth with advanced attachment and bone loss exhibit quantitative and qualitative differences in relation to gingivitis lesions at teeth with no attachment and bone loss. It is suggested that the large number and high density of plasma cells are the hallmarks of advanced periodontitis lesions and the most conspicuous difference in relation to long-standing gingivitis lesions.

Immunohistological analysis of CD1a langerhans cells and CD57 natural killer cells in healthy and diseased human gingival tissue: A comparative study

Background:

Cell interaction between dendritic cells (DC) and natural killer (NK) cells in the periodontal milieu is not yet fully known, although these cells are individually known to contribute to the pathogenesis of periodontal disease.

Materials and Methods:

Fifty subjects (25 males and 25 females) were included in the study. The subjects were divided into three groups: Group A comprised 16 subjects with clinically healthy gingiva; group B 17 subjects with gingivitis; and group C 17 subjects with gingivitis; and group C 17 subjects with moderate periodontitis (PPD ≥ 5 mm and CAL ≥ 3 mm in at least six sites). Gingival samples were collected and immunohistochemical study was done using CD57 and CD1a antibody. Statistical analysis was done using analysis of variance (ANOVA), followed by Tukey-Kramer multiple comparison for CD1a and Tukey's highly significant difference (HSD) test for CD57.

Results and Conclusion:

The study showed an inverse relationship between the CD1a⁺ (langerhans) cells and CD57⁺ (natural killer) cells. There was a significant increase in CD57⁺ cells and reduction in CD1a levels as periodontal disease progressed. The significant reduction in CD1a levels in periodontal disease when compared to health could possibly be a result of NK cells down regulating it. Reduction in CD1a levels may result in a low inflammatory response subsequently resulting in tissue destruction.

Are peri-implantitis lesions different from periodontitis lesions?

AIM

To compare histopathological characteristics of peri-implantitis and periodontitis lesions.

METHODS

A search was conducted on publications up to July 2010. Studies carried out on human biopsy material and animal experiments were considered.

RESULTS

While comprehensive information exists regarding histopathological characteristics of human periodontitis lesions, few studies evaluated peri-implantitis lesions in human biopsy material. Experimental peri-implantitis lesions were evaluated in 10 studies and three of the studies included comparisons to experimental periodontitis. Human biopsy material: the apical extension of the inflammatory cell infiltrate (ICT) was more pronounced in peri-implantitis than in periodontitis and was in most cases located apical of the pocket epithelium. Plasma cells and lymphocytes dominated among cells in both types of lesions, whereas neutrophil granulocytes and macrophages occurred in larger proportions in peri-implantitis.

EXPERIMENTAL STUDIES

placement of ligatures together with plaque formation resulted in loss of supporting tissues and large ICTs around implants and teeth. Following ligature removal, a "self-limiting" process occurred in the tissues around teeth with a connective tissue capsule that separated the ICT from bone, while in peri-implant tissues the ICT extended to the bone crest.

CONCLUSION

Despite similarities regarding clinical features and aetiology of peri-implantitis and periodontitis, critical histopathological differences exist between the two lesions.

Cynical hostility as a determinant of poor oral health status in an adult population

Our aim in this study was to determine whether there is an association between cynical hostility and clinically determined poor oral health, and whether this association is confounded by socioeconomic position and mediated by health behavior. The sample consisted of 4,207 dentate Finns, 30-64 yr of age. Oral health was measured in terms of numbers of missing teeth, of decayed teeth, and of teeth with periodontal pockets (> or = 4 mm). Cynical hostility was measured using the cynical distrust self-administered questionnaire. The subjects with the highest level of cynical hostility had fewer teeth, and a greater number of decayed teeth as well as teeth with deepened periodontal pockets compared to subjects with the lowest level of cynical hostility. The associations between cynical hostility and number of missing and decayed teeth were clearly confounded by level of education. Poor oral health behavior was shown to be a possible mediator between cynical hostility and number of decayed teeth, but not of missing teeth or teeth with deepened periodontal pockets. General health-related behavior did not serve as a possible mediator in any of the associations. In conclusion, cynical hostility can be considered as a risk marker for poor oral health. Interventions aimed to improve oral health should focus on psychosocial factors and on less-educated subjects.

Evidence for a specific crevicular lymphocyte profile in aggressive periodontitis

BACKGROUND AND OBJECTIVE

It is undisputed that the periodontal pocket is a particular region of the host defense that is dominated by polymorphonuclear leukocytes. However, little is known about the lymphocytes in the crevice. It was the aim of this study to analyse the proportions of T cells (CD3+), T-helper cells (CD4+), T-suppressor cells (CD8+), and B cells (CD20+) in the crevice of patients with localized aggressive periodontitis (LAP), generalized aggressive periodontitis (GAP), and generalized chronic periodontitis (CP). The results were compared with those obtained from periodontally healthy controls.

MATERIAL AND METHODS

Crevicular cells were collected according to a previously described method. The lymphocyte subpopulations were analysed by using an indirect immunofluorescence method.

RESULTS

Significant differences were established between the test groups and the controls regarding the mean number of CD8+ lymphocytes (LAP > CP and controls; p < 0.05) and CD20+ lymphocytes (LAP/GAP > CP, p < 0.05 and LAP/GAP > controls; p < 0.001). Significant variations in the CD4+/CD8+ ratio were observed (LAP < controls and GAP < controls; p < 0.01), as well as a correlation between the number of T cells and the degree of inflammation.

CONCLUSION

In the present study, patients with LAP and patients with GAP were found to have increased numbers of crevicular T-suppressor/cytotoxic and B cells. This supports the hypothesis of a changed immune pathology in patients with aggressive periodontitis.

Aspects of adaptive host response in periodontitis

OBJECTIVE

To review host response in periodontitis with respect to cellular composition of lesions, T cell receptor (TCR) gene expression, cytokine profiles of T-helper (Th) cells and autoimmune components.

MATERIAL AND METHODS

The studies included were confined to human material (biopsies, gingival crevicular fluid, blood from subjects with periodontitis).

RESULTS AND CONCLUSIONS

In periodontitis lesions, plasma cells are the most common cell type and represent about 50% of all cells, while B cells comprise about 18%. The proportion of B cells is larger than that of T cells and Th cells occur in larger numbers than T cytotoxic cells. Polymorphonuclear cells and macrophages are found in fractions of less than 5% of all cells. Lesions in aggressive and chronic forms of periodontitis exhibit similar cellular composition. Differences in disease severity, however, may reflect increases in plasma cell and B cell densities. B cells serve as important antigen-presenting cells in periodontitis. The periodontitis lesion expresses a unique TCR gene repertoire that is different from that in blood. The role of superantigens in periodontitis is unclear. There are few studies using comparative designs and unbiased quantitative methods regarding Th-1 and Th-2 cells in periodontitis. The relative dominance of B cells and plasma cells in periodontitis lesions cannot entirely be explained by enhanced Th-2 functions but maybe because of an imbalance between Th-1 and Th-2. Autoimmune reactions are evident in periodontitis lesions. The role of auto-antibodies in the regulation of host response in periodontitis, however, needs to be clarified. Auto-reactive B cells occur in larger proportions in subjects with periodontitis than in healthy controls.

Etiology and pathogenesis of periodontal diseases

The two most prevalent and most investigated periodontal diseases are dental plaque-induced gingivitis and chronic periodontitis. The last 10 to 15 years have seen the emergence of several important new findings and concepts regarding the etiopathogenesis of periodontal diseases. These findings include the recognition of dental bacterial plaque as a biofilm, identification and characterization of genetic defects that predispose individuals to periodontitis, host-defense mechanisms implicated in periodontal tissue destruction, and the interaction of risk factors with host defenses and bacterial plaque. This article reviews current aspects of the etiology and pathogenesis of periodontal diseases.

Relevance of Fc gamma RIIIa-158V-F polymorphism to recurrence of adult periodontitis in Japanese patients

The immunoglobulin receptor Fc gamma RIIIa (CD16) is distributed on natural killer (NK) cells, macrophages, and gamma delta T cells, and is polymorphic. Fc gamma RIIIa-158V has a higher affinity for both monomeric and immune complexed IgG1, IgG3, and IgG4 than IIIa-158F. We determined Fc gamma RIIIa-158V/F genotypes of Japanese patients with adult periodontitis. A significant over-representation of Fc gamma RIIIa-158F was found in patients with recurrence, compared with patients without recurrence, making Fc gamma RIIIA a candidate gene for recurrence risk of adult periodontitis.

Cell-mediated immune system regulation in periodontal diseases

The adaptive immune system consists of humoral and cell-mediated immunity. T-lymphocytes are the key components of cell-mediated immunity. CD4+ helper T-lymphocytes facilitate B-cells to differentiate and produce specific antibodies, whereas CD8+ cytotoxic T-lymphocytes kill virally infected cells. Periodontal diseases have been associated with a variety of imbalances in the regulation of immune responses. Changes in the ratios of peripheral blood CD4+ and CD8+ T-lymphocytes, depressed proliferative responses of peripheral blood lymphocytes, and increased frequency of CD45RO+ memory T-lymphocytes in diseased tissues have been reported in individuals with various forms of periodontal disease. While some studies have shown an increased frequency of gamma delta + T-cells in periodontal lesions, the role of gamma delta + T-cells in periodontal disease remains controversial. The ability of putative periodontopathic bacteria selectively to stimulate certain V beta-expressing T-cells is intriguing and could determine whether a CD4+ Th1 or a CD4+ Th2 cell response is elicited. The prominence of a particular subset of helper T-cells within the periodontal lesion could be a reflection of the stage and activity of the disease, or the types of bacteria present. Regardless, longitudinal studies of the involvement of T-cell subsets and cytokines in periodontal disease are clearly needed.

Presence of natural killer cells in human chronic periapical lesions

Natural killer (NK) cells are lymphoid in nature and appear to kill target cells (neoplastic and virus-infected cells) without apparent prior immunization. Ten human chronic periapical lesions were examined for the presence of these cells. The lesions were collected, frozen in liquid nitrogen, and sectioned. They were then stained with an indirect immunoperoxidase procedure for the presence of human NK cells. Human tonsils and human periapical scar tissue were used as positive and negative controls. The results showed absence of NK cells in scar tissue and the presence of NK cells in tonsils and all samples of human periapical lesions. NK cells may play a defensive role in controlling root canal infections or, possibly, a role in its pathogenesis.

Development and characterization of Porphyromonas gingivalis-specific rat T-cell clones

Porphyromonas gingivalis has been implicated as a major pathogen in periodontitis. To determine the role of T cells in the regulation of this disease, a method was developed for the generation and characterization of rat T-cell clones with antigen specificity to P. gingivalis whole cells. The clones studied so far demonstrated a T-helper (Th) phenotype W3/13+, W3/25+, OX8- and OX22-. These T-cell clones proliferated in vitro in response to P. gingivalis, but not to other bacteria (Prevotella intermedia, Actinobacillus actinomycetemcomitans, Wolinella recta, Fusobacterium nucleatum, Streptococcus sanguis). Limiting dilution analysis showed W3/25+, OX8- T cells preferentially respond to P. gingivalis, rather than W3/25-, OX8+ T cells. P. gingivalis-reactive W3/25+ T cells belonged to the OX22- population, suggesting that the OX22- T cells may represent memory cells. All clones tested produced interferon gamma, but not interleukin 2. The cloned T-cell F1 significantly enhanced P. gingivalis-specific antibody production (p < 0.03). The availability of these cloned T cells should bring new insight into the mechanism by which T cells regulate oral health and periodontal disease.

Activated lymphocyte subsets in adult periodontitis*

The activation state of T and B lymphocytes in the peripheral blood of periodontitis patients may be a reflection of disease activity. We have utilized 2- and 3-color flow cytometric analyses using a new chromophore, peridinin chlorophyll A protein, and conventional dyes, fluorescein isothiocyanate and phycoerythrin, conjugated to monoclonal antibodies against activated lymphocyte surface markers to measure blood lymphocyte subsets from 18 periodontitis patients and 16 periodontally healthy control subjects. Two-color flow cytometric analysis demonstrated that the frequency of CD4+ and CD5+ T cells, CD20+ B cells, and CD16+ NK (natural killer) cells were increased in periodontitis patients. Of particular interest, CD4+ activated "memory" T cells, CD5+ B cells, and CD56+ NK effector cells were increased significantly in periodontitis patients (p less than 0.05). While the relationship of lymphocyte activation to periodontal disease activity remains unclear, there may be potential for using 2- and 3-color flow cytometry to subcategorize periodontitis patients into high- and moderate-risk groups.

Ultrastructural evidence of large granular lymphocyte (LGL) activity in lesions of chronic adult periodontitis

The purpose of this investigation was to determine, on the basis of ultrastructural evidence, whether large granular lymphocyte (LGL)-mediated cytotoxic activity could be identified in lesions of chronic adult periodontitis. 18 gingival papilla biopsies were obtained from 8 adult patients, each satisfying the clinical criteria for chronic adult periodontitis. One-half of each biopsy was processed for examination by transmission electron microscopy (TEM). B-lymphocyte, T-lymphocyte, and NK-cell contributions to the inflammatory cell infiltrate were determined by subjecting the remaining one-half to the 3-layer avidin-biotin affinity immunoperoxidase technique. Immunohistochemistry using the anti-human leu-11b monoclonal antibody (representative of NK-cells which are known to comprise approximately 80% of the LGL population) showed that the Leu-11b+ population comprised 3-7% of the total monocytic infiltrate. The Leu-11b+ cells tended to occur as single cells or in small clusters of 3-12 cells. Generally, the Leu-11b+ cells exhibited perivascular locations situated subjacent to the epithelial basal lamina. TEM observations showed LGLs in intimate contact with fibroblasts that exhibited morphologic changes consistent with cellular damage or degeneration. In addition, LGLs were observed to exhibit apparent non-cytotoxic contacts with plasma cells, macrophages and other monocytic cells.