Assessment of Bone Viability After Heat Trauma: A Histological, Histochemical and Vital Microscopic Study in the Rabbit

In the present investigation a comparison was made between conventional histology, histochemistry and vital microscopy for assessment of heat-induced bone tissue injury. The extent of the bone damage around a burr hole or after heating fibular bone samples in saline solutions of various temperatures was evaluated by means of histology and histochemistry, using the absence of filled osteocyte lacunae or lack of oxidative enzyme activities as indication of bone death, respectively. In both cases a wider necrotic border zone was detected with histochemistry than with histology. The vital microscopic method is based on a titanium chamber which, after insertion in the rabbit tibia, allows observation and registration of the same bone compartment for a follow-up period of more than one year. The dynamic tissue events taking place after heating to 50 degrees C for one minute were investigated and compared with histological and histochemical data of the bone. The vital microscopic method showed a consistent and widespread bone tissue injury after heating to 50 degrees C for one minute while, on the other hand, the indirect methods exhibited only inconsistent signs of tissue injury. It is concluded that histochemistry using the presence or otherwise of diaphorase enzyme activities is a more reliable method than is histology for the estimation of bone viability after heat trauma. Vital microscopy is more sensitive than indirect, morphologic and metabolic techniques for detection of heat-induced bone tissue injury.

ACEs and counter-ACEs: How positive and negative childhood experiences influence adult health

BACKGROUND

Numerous studies over the past two decades have found a link between adverse childhood experiences (ACEs) and worse adult health outcomes. Less well understood is how advantageous childhood experiences (counter-ACEs) may lead to better adult health, especially in the presence of adversity.

OBJECTIVE

To examine how counter-ACEs and ACEs affect adult physical and mental health using Resiliency Theory as the theoretical framework.

PARTICIPANTS AND SETTING

Participants were Amazon mTurk users ages 19-57 years (N = 246; 42% female) who completed an online survey.

METHODS

We conducted a series of regression analyses to examine how counter-ACEs and ACEs predicted adult health.

RESULTS

Corresponding to the Compensatory Model of Resiliency Theory, higher counter-ACEs scores were associated with improved adult health and that counter-ACEs neutralized the negative impact of ACEs on adult health. Contrary to the Protective Factors Model, there was a stronger relationship between ACEs and worse adult health among those with above average counter-ACEs scores compared to those with below average counter-ACEs scores. Consistent with the Challenge Model, counter-ACEs had a reduced positive effect on adult health among those with four or more ACEs compared to those with fewer than four ACEs.

CONCLUSIONS

Overall, the findings suggest that counter-ACEs protect against poor adult health and lead to better adult wellness. When ACEs scores are moderate, counter-ACEs largely neutralize the negative effects of ACEs on adult health. Ultimately, the results demonstrate that a public health approach to promoting positive childhood experiences may promote better lifelong health.

Initial versus deferred melphalan-prednisone therapy for asymptomatic multiple myeloma stage I--a randomized study. Myeloma Group of Western Sweden

From October 1983 until December 1988, 50 patients with asymptomatic multiple myeloma stage I were included in a prospective randomized multi-centre study comparing melphalan-prednisone (MP) therapy started at the time of diagnosis with deferred therapy where MP was started at the time of disease progression. Twenty-five patients were randomized to each group. The median time from diagnosis to start of therapy in the group with deferred therapy was 12 months. The reasons for starting therapy were increasing M-protein in 8 cases, symptomatic bone disease in 9 and anaemia in 5. In 2 cases, disease progression was complicated by vertebral fractures necessitating radiotherapy. Two patients in the group in which MP was started at the time of diagnosis developed acute leukaemia. No differences in response rate, response duration or survival were observed between the treatment groups. We conclude that in asymptomatic myeloma deferral of chemotherapy is feasible in well-informed and well-controlled patients but conveys no advantage in survival. In clinical practice the benefits of treatment deferral are to some extent outweighed by disease progression before start of treatment.

Metal sensitivity in patients with metal-to-plastic total hip arthroplasties

Out of 134 patients patch tested after total hip replacement (metal-to-plastic) 13 were sensitive to one or two of the implanted metals. In a prospective series of 112 patients, nine were sensitive to nickel before and another three developed sensitivity to nickel or cobalt after the arthroplasty. In the retrospective as well as in the prospective series the complications could in all cases but one be explained on grounds other than allergy. The incidence of contact allergy to nickel before a planned arthroplasty was 12 per cent in females and 4 per cent in males. It is doubtful whether metal sensitivity could be induced by a total hip arthroplasty. However, in cases of a preexisting metal allergy, a certain degree of caution is recommended.

A longitudinal study of serum TSH, and total and free iodothyronines during normal pregnancy

Serum T4, T3, rT3, free T4, free T3 and TSH were measured during and after normal pregnancy in 20 women. Special methodological precautions were taken to avoid interference of other hormones and protein alterations in the assays. Serum T4 and T3 were steadily increasing during the last part of the 1st trimester, and remained high and nearly stable during the 2nd and 3rd trimester of the gestation period. The high levels were approximately 1.5 times the values measured 10 weeks post-partum. Serum rT3 was elevated already during the last part of the 1st trimester and remained high throughout pregnancy, compared to the post-partum value. Serum free T4 and free T3 were slightly elevated in early pregnancy. The values decreased gradually during pregnancy and were slightly depressed during the 3rd trimester. A gradual increase in serum TSH was observed during pregnancy and the 2nd and 3rd trimester values were significantly higher than the post-partum value. The mean values for serum TSH, free T4 and free T3 remained always well within the normal range. Thus small variations in serum free iodothyronines and TSH occur during normal pregnancy, the alterations observed in the last trimester of the gestation period resembling those of a slight thyroid insufficiency. These trends in variation of the reference values are worth to remember in the diagnosis of borderline hypo- or hyperthyroidism and in the balanced treatment of pregnant women with thyroid dysfunction.

Veterinary drug delivery: potential for skin penetration enhancement

A range of topical products are used in veterinary medicine. The efficacy of many of these products has been enhanced by the addition of penetration enhancers. Evolution has led to not only a highly specialized skin in animals and humans, but also one whose anatomical structure and skin permeability differ between the various species. The skin provides an excellent barrier against the ingress of environmental contaminants, toxins, and microorganisms while performing a homeostatic role to permit terrestrial life. Over the past few years, major advances have been made in the field of transdermal drug delivery. An increasing number of drugs are being added to the list of therapeutic agents that can be delivered via the skin to the systemic circulation where clinically effective concentrations are reached. The therapeutic benefits of topically applied veterinary products is achieved in spite of the inherent protective functions of the stratum corneum (SC), one of which is to exclude foreign substances from entering the body. Much of the recent success in this field is attributable to the rapidly expanding knowledge of the SC barrier structure and function. The bilayer domains of the intercellular lipid matrices within the SC form an excellent penetration barrier, which must be breached if poorly penetrating drugs are to be administered at an appropriate rate. One generalized approach to overcoming the barrier properties of the skin for drugs and biomolecules is the incorporation of suitable vehicles or other chemical compounds into a transdermal delivery system. Indeed, the incorporation of such compounds has become more prevalent and is a growing trend in transdermal drug delivery. Substances that help promote drug diffusion through the SC and epidermis are referred to as penetration enhancers, accelerants, adjuvants, or sorption promoters. It is interesting to note that many pour-on and spot-on formulations used in veterinary medicine contain inert ingredients (e.g., alcohols, amides, ethers, glycols, and hydrocarbon oils) that will act as penetration enhancers. These substances have the potential to reduce the capacity for drug binding and interact with some components of the skin, thereby improving drug transport. However, their inclusion in veterinary products with a high-absorbed dose may result in adverse dermatological reactions (e.g., toxicological irritations) and concerns about tissue residues. These are important considerations when formulating a veterinary transdermal product when such compounds are added, either intentionally or otherwise, for their penetration enhancement ability.

The Swedish snus and the Sudanese toombak: are they different?

In Sweden, snuff (locally known as snus), was introduced since the year 1637. Presently, Sweden has the highest per capita consumption and sale figures of snuff in the world, and the habit is becoming increasingly popular. Snus is manufactured into a dry form used in the nasal cavity and a moist form used in the oral cavity. Snus manufactured for oral use is a moist ground tobacco of Dark Kentucky or Virginia species mixed with an aqueous solution of water and other blending ingredients. This form of snuff is found in two types: (1) loose and (2) portion-bag-packed. These are the most widely used. The loose moist form (1-2 g a quid) is the most popular type consumed by 73% of the males, followed by the portion-bag-packed form (0.5-1 g a quid), consumed by 13% of the males, while 14% of the males are mixed users. The majority of snus users place the quid in the vestibular area of the upper lip, and the prevalence among persons 15 years of age or older in 15.9% among males and 0.2% among females. The pH of snus has declined from a previous range of 8-9 to a range of 7.8-8.5, moisture content ranges 35-60% and nicotine content is in the order of 5-11 mg/g dry wt tobacco-specific N-nitrosamines (TSNAs) in micrograms (N'-nitrosonornicotine: NNN 5-9; 4-(methyl-nitrosamino)-1-(3-pyridyl)-1-butanone: NNK 1-2; N'-nitrosoanatabine: NAT 2-5). In the Sudan, snuff, locally known as toombak, was introduced approximately 400 years ago. It is always processed into a loose moist form, and its use is widespread in the country. Tobacco used for manufacture of toombak is of the species Nicotiana rustica, and the fermented ground powder is mixed with an aqueous solution of sodium bicarbonate. The resultant product is moist, with a strong aroma, highly addictive and its use is widespread particularly among males. Its pH range is 8-11, moisture content ranges 6-60% and nicotine content is from 8 to 102 mg/g dry wt, and TSNAs contents in micrograms (NNN 420-1 550; NNK 620-7 870; NAT 20-290). Snus and toombak dippers develop a clinically and histologically characteristic lesion at the site of dipping. Probably due to control of the TSNAs in snus, this type of snuff is associated with a lower risk of cancer of the oral cavity (relative risk: RR 5-6-fold), whereas the risk for cancer of the oral cavity among toombak users was high (RR 7.3-73.0-fold). In conclusion, the two snuff products significantly differ in many aspects. Most notable differences are tobacco species, fermentation and ageing, nicotine and TSNAs content, pH, expression of the p53 tumour suppressor gene, and keratin types 13, 14, and 19. It was, therefore, the object of the present study to highlight the oral health hazards of toombak, and to compare it with snus regarding the aforementioned differences.

Progression of sialadenitis in Sjögren's syndrome

An analysis of progression of sialadenitis in patients with primary and secondary SS has been performed. For this purpose patients were prospectively followed and evaluated with respect to stimulated whole salivary secretion and morphology of labial salivary gland biopsies. Twenty-one patients with primary SS and 18 with secondary SS were followed for a mean of 39 +/- 20 months (range 11-112 months). During this observation period the lymphocytic infiltration in minor salivary glands, measured as focus score, increased in 14/21 (67%) patients with primary SS and in 14/18 (78%) patients with secondary SS. Altogether there was a statistically significant increase in focus score in both primary and secondary SS, but no reduction in salivary production. Consequently, no correlation between changes in focus score and stimulated salivary secretion was found in either primary or secondary SS.

Odontogenic myxoma--a radiographic study of 21 tumours

Radiological features of 21 odontogenic myxomas found in 14 women and 7 men were analysed. Ten of the tumors were unilocular and 11 were multilocular. Unilocular lesions were mostly located in the anterior and multilocular in the posterior areas of the jaws. Intralesional trabeculation was seen in all multilocular but only in 3 unilocular lesions. Because radiological appearance of myxoma may be essentially similar with many other lesions of the jaws careful radiological examination is mandatory for planning of proper treatment.

Early age at first intercourse and subsequent gaps in contraceptive use

BACKGROUND

Sexual debut before age 15 years has been associated with increased sexual risk behaviors among teens, but little is known about its effects beyond adolescence. This study examines the relationship between the age at first intercourse and subsequent contraceptive gaps.

METHODS

We identified 3538 sexually active, fertile women participants from the 2006-2008 National Survey of Family Growth. Women were classified as consistent contraceptive users or inconsistent/nonusers. Age at first intercourse with a man was determined by self-report and categorized as <15, 15-17, and ≥18 years.

RESULTS

Twenty-three percent reported gaps in contraceptive use in the year prior to interview. Compared with women who were 18 or older at first intercourse, women who were <15 years of age at the time of first intercourse were nearly two times as likely to report a gap in contraceptive use (adjusted odds ratio: 1.93; 95% confidence interval: 1.23-3.00).

CONCLUSIONS

Age at first intercourse is associated with inconsistent or nonuse of contraceptives in later life. Primary prevention efforts should be established to empower girls to make informed and autonomous decisions about sexual debut. Personalized contraceptive counseling has been demonstrated as being effective in increasing contraceptive use and compliance and should be offered to all women, with particular focus on women who report an early age at first intercourse or other factors associated with inconsistent contraceptive use.

Iron losses in sweat

The losses of iron in whole body cell-free sweat were determined in eleven healthy men. A new experimental design was used with a very careful cleaning procedure of the skin and repeated consecutive sampling periods of sweat in a sauna. The purpose was to achieve a steady state of sweat iron losses with minimal influence from iron originating from desquamated cells and iron contaminating the skin. A steady state was reached in the third sauna period (second sweat sampling period). Iron loss was directly related to the volume of sweat lost and amounted to 22.5 micrograms iron/l sweat. The findings indicate that iron is a physiological constituent of sweat and derived not only from contamination. Present results imply that variations in the amount of sweat lost will have only a marginal effect on the variation in total body iron losses.

The influence of adverse and advantageous childhood experiences during adolescence on young adult health

BACKGROUND

Research indicates that adverse childhood experiences (ACEs) can lead to poorer adult health, but less is known how advantageous childhood experiences (counter-ACEs) may neutralize the negative effects of ACEs, particularly in young adulthood.

PURPOSE

We examined the independent contributions of Adverse Childhood Experiences (ACEs) and Advantageous Childhood Experiences (counter-ACEs) that occur during adolescence on five young adult health indicators: depression, anxiety, risky sexual behaviors, substance abuse, and positive body image.

PARTICIPANTS AND SETTING

The sample included 489 adolescents from a large northwestern city in the United States who were 10-13 years at baseline (51 % female).

METHODS

Flourishing Families Project survey data were used for this secondary analysis using structural equation modeling. Adolescents and their parents completed an annual survey. ACEs and counter-ACEs were measured over the first five years of the study. The five health indicators were measured in wave 10 when participants were 20-23 years old.

RESULTS

Participants had on average 2.7 ACEs and 8.2 counter-ACEs. When both ACEs and counter-ACEs were included in the model, ACEs were not predictive of any of the health indicators and counter-ACEs were predictive of less risky sex (-.12, p < .05), substance abuse (-.12, p < .05), depression (-.11, p < .05), and a more positive body image (.15, p < .01). Higher ratios of counter-ACEs to ACEs had a particularly strong effect on improved young adult health.

CONCLUSIONS

Counter-ACEs that occur in adolescence may diminish the negative effects of ACEs on young adult health and independently contribute to better health.

Karyotypic evolution in Ph-positive chronic myeloid leukemia in relation to management and disease progression

In a prospective study of 32 patients with chronic myeloid leukemia the frequency of chromosome abnormalities in addition to the Philadelphia chromosome (Ph) increased when the disease progressed. Before metamorphosis, 10 patients (31%) had developed additional abnormalities. Such abnormalities were present in three of them at the time of diagnosis; in the other seven, they were detected late in the chronic phase. New clonal abnormalities heralded or accompanied a more malignant phase of the disorder, usually a blastic leukemia. During metamorphosis, 78% of the patients had additional abnormalities, which in 68% of these cases comprised at least one of +8, +22q- or i(17q). Clones with additional abnormalities disappeared in eight cases, either spontaneously or in association with cytostatic therapy during the chronic or blastic phase. Involvement of chromosome #8, usually in the form of a trisomy, was found in 7 of 12 patients treated with busulfan, but was not found in any of the 10 hydroxyurea-treated patients, of whom 8 were splenectomized early during the chronic phase. Cells from the spleen, obtained by fine needle aspiration or splenectomy were cytogenetically examined in 18 cases during the chronic phase, but abnormalities in addition to the Ph were noted in only one patient, who was examined in the late chronic phase. The same abnormalities were present in bone marrow cells of this patient.

Cinnamic aldehyde in toothpaste. 1. Clinical aspects and patch tests

Although cinnamon is known to cause dermatitis in bakers and confectioners, it has only rarely been reported as causing trouble in food or cosmetics. A newly-formulated 'spicy' toothpaste containing cinnamon as a flavouring agent was the cause of oral symptoms in eight patients referred to clinics in Buckinghamshire and in Malmö and in a further eight patients discovered subsequently. Similar symptoms and patch test results were observed independently at both centres. Positive reactions were obtained with 1% cinnamic aldehyde in 15 out of 16 patients tested. Only one patient reacted to a standard sample of balsam of Peru (25% in petrolatum).

Identification of contact sensitizers by animal assay

Guinea pig testing constitutes the first step in evaluating the allergenicity of new chemicals and products. Some of the most commonly used animal predictive tests are reviewed. The guinea pig maximization test, which is the recommended test method in Sweden, is described in detail and the interpretation of results obtained with this test is discussed. In the guinea pig maximization test the sensitization capacity of a substance is examined by the use of maximized conditions for the exposure, i.e. the potential ability of the material to induce a contact allergy is determined. The extent to which an allergen causes contact dermatitis in exposed persons depends on the mode of use and various environmental factors.

Percutaneous Absorption of Steroids: Determination of in vitro Permeability and Tissue Reservoir Characteristics in Human Skin Layers

The skin localization of steroids following topical application is largely unknown. We determined the distribution of five steroids in human skin using excised epidermal, dermal, and full-thickness membranes in vitro. There was no significant difference in steroid maximum flux through epidermal and full-thickness membranes, other than significantly lower fluxes for the most polar steroid, aldosterone. Hydrocortisone had the highest dermal diffusivity and dermal penetration, and the accumulation of hydrocortisone and corticosterone was higher than that of the other steroids. Slower penetration and higher accumulation in the viable epidermis of progesterone in full-thickness skin were consistent with dermal penetration limitation effects associated with high lipophilicity.

Myxoid variant of follicular dendritic cell sarcoma arising in the breast

Follicular dendritic cell sarcoma is a malignant tumor of the follicular dendritic cell which can arise in extranodal sites. We present here a case arising as a mass in the breast of a 41-year-old woman. The tumor was composed of mildly pleomorphic spindly cells with pale ovoid nuclei and cell processes intimately admixed with mature lymphocytes. In much of the lesion the cells were dispersed in cords in a myxoid stroma, and elsewhere there were solid sheets. The neoplastic cells were immunoreactive for CD21, CD35, EMA, and S100 protein, but not for other lymphoid markers or cytokeratin. Electron microscopy showed interdigitating cytoplasmic processes with junctions but no external lamina. The differential diagnosis includes carcinoma, lymphomas, and a variety of myxoid sarcomas. The tumor recurred within a few months and displayed increased nuclear pleomorphism and lymphatic invasion but the patient appears free of disease 3 years after the further excision. This case extends the spectrum of follicular dendritic cell sarcoma in soft tissue sites.

Prevalence of iron deficiency and iron overload in the adult Icelandic population

The aim of this cross-sectional study was to estimate the prevalence of iron deficiency and overload in the adult population in Iceland, a developed Scandinavian country. The study population consisted of 4240 individuals aged 25-74 years randomly selected from the national roster. Basic hematological, S-iron, S-total iron binding capacity (TIBC), and S-ferritin measurements were obtained on 2588 individuals (61.0%). The results indicated unusually large iron stores in the adult Icelandic population and significantly larger iron stores in the rural compared to the urban population. Iron deficiency was rare except in urban premenopausal women, where 1 in 4 showed evidence of iron deficiency and 3.2% had iron deficiency anemia. Seven patients with hereditary hemochromatosis were identified from a subgroup of 1887 subjects, resulting in a prevalence of 0.37%. Two of the hereditary hemochromatosis patients had been gastrectomized. Measures to improve the iron balance in urban premenopausal women cannot therefore include increased iron fortification of food but must be more directed towards the target group.

Initial treatment in multiple myeloma: no advantage of multidrug chemotherapy over melphalan-prednisone. The Myeloma Group of Western Sweden

From October 1983 until December 1986, 164 patients with multiple myeloma stage II-III were included in a prospective randomized multi-centre study comparing melphalan-prednisone (MP) with multidrug chemotherapy (MDC). The patients comprised 77% of all newly diagnosed myeloma stage II-III cases reported from 18 hospitals covering the entire Health Care Region of Western Sweden (1.5 million inhabitants). Patients randomized to MP (29 stage II and 55 stage III patients) were given oral melphalan and prednisone every 6 weeks. For patients randomized to MDC, stage II patients (n = 25) were given VMCP every 4 weeks and stage III patients (n = 53) VBAP and VMCP alternately every 4 weeks. For stage II patients, the response rate for MP compared to VMCP was 69 versus 56% and the median survival 46 versus 33 months. For stage III the response rate for MP compared to VBAP/VMCP was 58 versus 57% and the median survival 26 versus 24 months. No statistically significant differences were seen. The time to response and remission duration were also similar in both treatment arms. The dose intensity index (cumulative given/planned dose of myelosuppressive drugs) was greater than or equal to 0.8 in 89% of the MP patients and 81% of the MDC patients. Patients with index values less than 0.8 had the same response rate as patients with index greater than or equal to 0.8. This study has not demonstrated any advantage of MDC over traditional MP in multiple myeloma stage II-III.

Langerhans cells and T cells sense cell dysplasia in oral leukoplakias and oral squamous cell carcinomas--evidence for immunosurveillance

Leukoplakias (LPLs) are lesions in the oral mucosa that may develop into oral squamous cell carcinoma (OSCC). The objective of this study was to assess presence and distribution of dendritic Langerhans cells (LCs) and T cells in patients with LPLs with or without cell dysplasia and in oral squamous cell carcinoma (OSCC). Biopsy specimens from patients with leukoplakias (LPLs) with or without dysplasia and oral squamous cell carcinoma (OSCC) were immunostained with antibodies against CD1a, Langerin, CD3, CD4, CD8 and Ki67, followed by quantitative analysis. Analyses of epithelium and connective tissue revealed a significantly higher number of CD1a + LCs in LPLs with dysplasia compared with LPLs without dysplasia. Presence of Langerin + LCs in epithelium did not differ significantly between LPLs either with or without dysplasia and OSCC. T cells were found in significantly increased numbers in LPLs with dysplasia and OSCC. The number of CD4+ cells did not differ significantly between LPLs with and without dysplasia, but a significant increase was detected when comparing LPLs with dysplasia with OSCC. CD8+ cells were significantly more abundant in OSCC and LPLs with dysplasia compared with LPLs without dysplasia. Proliferating cells (Ki67+) were significantly more abundant in OSCC compared to LPLs with dysplasia. Confocal laser scanning microscopy revealed colocalization of LCs and T cells in LPLs with dysplasia and in OSCC. LCs and T cells are more numerous in tissue compartments with dysplastic epithelial cells and dramatically increase in OSCC. This indicates an ongoing immune response against cells with dysplasia.

Political and personal reactions to COVID-19 during initial weeks of social distancing in the United States

OBJECTIVE

To examine perceptions, behaviors, and impacts surrounding COVID-19 early in the pandemic response.

MATERIALS AND METHODS

A cross-sectional survey of 1,030 U.S. adults was administered on March 31st, 2020. This survey examined attitudes toward media, government, and community responses to COVID-19 by political ideology and sociodemographic factors. Knowledge, anxieties, and impacts of COVID-19 were also assessed.

RESULTS

Conservatives were more likely to report that COVID-19 was receiving too much media coverage and people were generally overreacting; liberals were more likely to report the government had not done enough in response to the pandemic. Females and those with lower income experienced more COVID-19 related economic anxieties. Those working and with children at home reported higher social, home, and work disruption. Social distancing behaviors were more common among liberals and were associated with increases in depressive symptoms. General knowledge about COVID-19 was widely exhibited across the sample, however, Black and Hispanic respondents were less likely to correctly answer questions about the availability of a vaccine and modes of transmission.

CONCLUSIONS

Public health experts should consider the political climate in crafting messaging that appeals to the values of those across the political spectrum. Research on the COVID-19 pandemic should continue to monitor the effects of social distancing on mental health and among vulnerable populations.

Expression of Class II transplantation antigens by epithelial cells in oral candidosis, oral lichen planus and gingivitis

Biopsies from normal oral mucosa and oral mucosa affected by candidosis, lichen planus or gingivitis were compared with respect to the expression of two Class II transplantation antigens, HLA-DR and HLA-DQ, by epithelial cells and the relationship of these antigens to the distribution and frequency of T-lymphocytes. Indirect immunohistochemistry with different mouse monoclonal antibodies was used on frozen and acetone-fixed sections. To evaluate the results, a score system based upon the expression of the Class II transplantation antigens by epithelial cells and the frequency of T-lymphocytes was used. In oral candidosis there was a marked expression of HLA-DR antigens throughout the epithelium. In addition, this type of epithelium was the only one that expressed HLA-DQ antigens. An intense intraepithelial infiltration of T-lymphocytes was observed. Oral lichen planus and gingivitis did, to a much lesser extent, cause the expression HLA-DR antigens by the epithelial cells. In both lesions, the number of T-lymphocytes within the epithelium did not exceed the number found in epithelium of normal mucosa. In these types of lesions, the subepithelial infiltrate varied in intensity but was mainly composed of T-lymphocytes reactive with anti-Leu 3a antibodies. The results of the present study imply that epithelial expression of the two different Class II antigens are related to the frequency of the T-lymphocytes and to the proximity of these cells to the epithelial cells.