Effect of cepharanthin on superoxide anion (O2-) production by macrophages

Our previous report showed the inhibitory action of cepharanthin on oxygen-derived free radical production by polymorphonuclear leukocytes (PMN). In the present study, we examined the effects of cepharanthin on production of superoxide anion (O₂^–), one oxygen radical, by macrophages in vitro and in vivo. Phorbol myristate acetate-induced O₂^– production by mouse peritoneal exudate cells (PEC), whose constituent cell types were identified as macrophages, lymphocytes, and PMN (75, 20, and less than 5%, respectively), was measured by ferricytochrome C reduction assay. Superoxide anion production by PEC, which depended mainly on the macrophage component, was inhibited 34% by 5 μg/ml cepharanthin and 85% by 50 μg/ml. These results indicate that cepharanthin suppresses O₂^– production by macrophages as well as by PMN. The fact that no inhibition of O₂^– by a xanthine-xanthine oxidase system was observed indicates that cepharanthin is not a scavenger of O₂^–. Carrageenan-induced paw edema is due to the activity of macrophages. Participation of O₂^– and other oxygen radicals is implicated in this edema, because the swelling is inhibited by administration of superoxide dismutase. The effects of cepharanthin on O₂^– production by macrophages was examined using this experimental system in mice. However, no significant inhibition of the edema by cepharanthin was observed.     

Augmented telomerase activity and reduced telomere length in parthenium‐induced contact dermatitis

Background Parthenium dermatitis is a common chronic inflammatory disease with activated T lymphocytes that recognize the antigens, which leads to proliferation and differentiation. Telomeres and telomerase play an important role in the regulation of life span of the cell. Telomere length maintained by telomerase, are specialized repeats present at the end of chromosomes which protect it from degradation, end‐to‐end fusion and are important for integrity of chromosomes. Objectives The aim of this study was to measure telomerase activity and telomere length in Peripheral blood mononuclear cell (PBMC), CD4⁺ and CD8⁺ T lymphocytes from parthenium dermatitis patients. Methods The study includes 50 patients of parthenium dermatitis confirmed by patch testing and 50 healthy controls. Telomerase activity was measured using the telomere repeat amplification protocol using PCR–ELISA kit. Telomere length was measured by using Telo TAGGG Telomere Length Assay Kit. Results Significantly elevated levels of telomerase activity was observed in PBMC, CD4⁺ and CD8⁺ T cells of parthenium dermatitis patients as compared with healthy controls. However, significantly reduced telomere length in PBMC, CD4⁺ and CD8⁺ T cells have been found in patients than healthy subjects, but there was no difference between CD4⁺ and CD8⁺ T cells in patients. Conclusion This study might have provided insight into the role of telomerase in parthenium dermatitis that is characterized by the recruitment of T lymphocytes, which play an important role in this inflammatory disease. The augmented telomerase activity and reduced terminal restriction fragment length might be explored as a potential diagnostic/prognostic marker for parthenium dermatitis in future.     

HISTIDINE-RICH PROTEIN AS A POSSIBLE ORIGIN OF FREE AMINO ACIDS OF STRATUM CORNEUM

Pulse-chase labeling experiments with ³H-histidine and ³H-arginine were performed in hairless mice to investigate the origin of free amino acids in the stratum corneum. Time-course labeling of epidermal proteins was examined by sodium dodecyl sulfate-polyacryl amide gel electrophoresis (SDS-PAGE). The radioactivity was also measured in the following three epidermal fractions; 0.1 N HClO₄ soluble-ethanol soluble fraction (Fr. I), 0.1 N HClO₄ soluble-ethanol insoluble fraction (Fr. II, histidine-rich protein fraction) and 0.1 N HClO₄ insoluble-8M urea soluble fraction (Fr. III). Labeled amino acids were rapidly incorporated into Fr. III, especially into a particular protein which showed little mobility on SDS-PAGE. As the radioactivity of this protein decreased, an increase in radioactivity was observed in a 32,000 MW histidine-rich protein, the only major protein in Fr. II. The radioactivity of 32,000 MW protein then fell, accompanied by an increase in radioactivity of Fr. I. The major radioactive substances in Fr. I were identified as ³H-histidine and ³H-urocanic acid after ³H-histidine injection and as ³H-arginine after ³H-arginine injection. The amino acid composition of the histidine-rich protein was very similar to the composition of free amino acids of the stratum corneum, in which amino acid metabolites were considered as their precursor amino acids. These results suggested that the free amino acids of the stratum corneum might be a final product of the degradation of histidine-rich protein.     

In vitro analysis of the phenotypical and functional properties of the 4F7+ cutaneous accessory dendritic cell

The monoclonal antibody 4F7 detects a molecule on dermal and epidermal Ia⁺ dendritic cells (DCs), and some of these cells are Birbeck granule-containing cells. Here we report on the phenotypical and functional characteristics of these cells which were highly enriched by 4F7-labelled immunomagnetic beads. The ultrastructural, immunocytochemical and cytochemical analyses of these preparations showed cells with the typical characteristics of DCs. The cells were found to express the DC marker NLDC145, but not 33D1. The C3bi receptor and marker F4/80 were only expressed by epidermal 4F7⁺ cells. The capacity of freshly isolated 4F7⁺ epidermal and dermal DCs to activate allogeneic T cells in a mixed leukocyte reaction was similar to the capacity of freshly isolated Langerhans cells. After culture, the epidermal cells showed a 4–5-fold increase in stimulation, whereas no difference was observed in the 4F7⁺ dermal DCs. We conclude that this new antibody recognizes a function-associated molecule on cutaneous DCs which are phenotypically and functionally related to Langerhans cells. The 4F7⁺ DCs may be precursors of epidermal Langerhans cells.Part of this work was presented at the 21st Annual Meeting of the ESDR, Copenhagen, 1991, and the Third International Workshop on Langerhans Cells, Dallas, 1991     

Treatment of severe psoriasis with low dose cyclosporin A and the effect on the helper-suppressor T cell ratio in peripheral blood

Oral administration of cyclosporin A (CsA) 14 mg/kg/day has been reported to improve psoriasis in a double-blind study. The purpose of this study was to evaluate the efficacy of a lower dose of CsA in severe psoriasis and to monitor lymphocyte subpopulations in peripheral blood in order to detect its mechanism of action. Eleven patients with severe, active psoriasis were treated only with oral administration of 5 mg/kg/day CsA twice a day for 3 months, during which they were closely examined, including single- and two-color analysis of lymphocyte surface markers by flow cytometry using monoclonal antibodies. Seven patients showed improvement within a week, and the others within 2-3 weeks. Five patients had total remission, 2 showed marked improvement, and 4 showed moderate improvement; no clinically important side effects, except hypertrichosis in 2 females were seen. In the peripheral blood of patients treated with CsA there was a decrease in the percentages of helper inducer (CD4⁺4B4⁺)T(Thi) cells, while no significant decrease was found in those of suppressor inducer (CD4⁺2H4⁺)T(Tsi), suppressor effector (CD8⁺CD11⁺)T(Tse), or cytotoxic (CD8⁺CD11^-)T(Tc) cells, resulting in a decrease in the ratio of Thi to Tsi, Tse and Tc. The activated helper (CD4⁺HLA-DR⁺)—suppressor (CD8⁺HLA-DR⁺)T cell ratio was also decreased. These immunological findings obtained from the patients were consistent with in vitro studies of CsA reported earlier and may well explain the effectiveness of CsA in psoriasis as observed in this study.     

UVA does not photoreactivate pyrimidine dimers in cultured human fibroblasts

Abstract Pyrimidine dimers were induced in duplicates of cultured human skin fibroblasts by irradiation with various doses of UVB radiation. Subsequently, one set of cells was further exposed to either 5 or 10 J/cm² of UVA radiation to assess the photoreactivating activity of this spectral range in a human cell system. Following irradiation, pyrimidine dimers were quantified in all cells by determining the number of endonuclease-sensitive sites (ESS). No difference in the yield of ESS was observed between cells which had been irradiated with UVB only as compared to cells which subsequently had been exposed to 5 or 10 J/cm² UVA. In contrast, subsequent exposure of UVB-irradiated cells of Monodelphis domestica to 10 J/cm² UVA resulted in an almost 50% reduction of UVB-induced pyrimidine dimers. These data indicate that UVA does not induce photoenzymatic repair in human fibroblasts.     

Induction of tolerance by administration of hapten-immunoglobulin conjugates is associated with decreased IL-2 and IL-4 production

Intravenous administration of trinitrophenyl-modified isologous immunoglobulin-induced nonresponsiveness to subsequent epicutaneous painting of sensitizing doses of trinitrochlorobenzene. Isologous immunoglobulin with various degrees of trinitro-phenyl substitution (11.2, 14.3, 27 and 47.3) prevented sensitization. The suppression of contact hypersensitivity was dependent on the dose of tolerogen and was hapten specific. Tolerance was inducible in mice of the strains CBA (H-2^k), C57BL/6 (H-2^b), and DBA/2 (H-2^d) but not in Balb/C (H-2^d) mice, suggesting that this trait maps outside the murine major histocompatibility complex. Tolerance induced by trinitro-phenyl-modified immunoglobulin was associated with decreased hapten-induced proliferation of draining lymph-node cells. Unlike in other models of tolerance in which a decreased interleukin-2 to interleukin-4 ratio can be observed, administration of tolerizing trinitrophenylated immunoglobulin was associated with deficient hapten-induced release of both interleukin-2 and interleukin-4.     

Effects of microdermabrasion on skin rejuvenation

Abstract

Background: Microdermabrasion is a surface treatment, noninvasive, which uses a negative pressure and drives programmable inert microcrystals on the skin, causing an exfoliation. Objective: The aim of this study was to evaluate the effects of application of microdermabrasion in human skin rejuvenation. Methods: Eleven women who were undergoing abdominoplasty were considered. An area of 25 cm² in the umbilicus to the right was conditioned with microcrystals of Al₂O₃ in maximum flow, negative pressure of 200 mmHg and total of 8 past, the left side being used as control. The number of sessions ranged from one to five, with weekly intervals, and timing of sample collection ranged from 0 to 132 days. Samples were fixed in 10% formaldehyde in phosphate buffer and were evaluated histologically. Results: A mild to marked hyperpigmentation was observed and remained for a variable period. Histological findings suggest an improvement in the epidermal layer with increased thickness and reestablishing their interdigitations in the dermis initially observed an increase in collagen synthesis. The analysis showed a late stay of epidermal changes, which did not occur in the dermis. Conclusion: Under the conditions and parameters used in this work, the microdermabrasion had a positive skin structure, showing that a viable resource in promoting skin rejuvenation.     

Increase of interleukin‐10‐producing B cells associated with long‐term remission after i.v. immunoglobulin treatment for pemphigus

We present a refractory case of pemphigus vulgaris that achieved long‐term remission after i.v. immunoglobulin treatment (IVIG). We evaluated the fluctuation of circulating interleukin‐10‐producing B cells (B10 cells) during the course in our case and other three patients with pemphigus treated with IVIG without clinical remission. B10 cells were observed predominantly in CD1d^–, CD5^–, CD9^– and CD27⁺ populations among CD19⁺ cells in healthy controls, as well as in patients with pemphigus. The frequency of B10 cells among CD19⁺ cells increased in our case, but not in the other three patients without clinical remission, which leads to speculation on the association between the increase of B10 cells and the achievement of long‐term remission after IVIG treatment.     

The skin microbiome of caspase‐14‐deficient mice shows mild dysbiosis

Caspase‐14, an important proteinase involved in filaggrin catabolism, is mainly active in terminally differentiating keratinocytes, where it is required for the generation of skin natural moisturizing factors (NMFs). Consequently, caspase‐14 deficient epidermis is characterized by reduced levels of NMFs such as urocanic acid and 2‐pyrrolidone‐5‐carboxylic acid. Patients suffering from filaggrin deficiency are prone to develop atopic dermatitis, which is accompanied with increased microbial burden. Among several reasons, this effect could be due to a decrease in filaggrin breakdown products. In this study, we found that caspase‐14^?/? mice show enhanced antibacterial response compared to wild‐type mice when challenged with bacteria. Therefore, we compared the microbial communities between wild‐type and caspase‐14^?/? mice by sequencing of bacterial 16S ribosomal RNA genes. We observed that caspase‐14 ablation leads to an increase in bacterial richness and diversity during steady‐state conditions. Although both wild‐type and caspase‐14^?/? skin were dominated by the Firmicutes phylum, the Staphylococcaceae family was reduced in caspase‐14^?/? mice. Altogether, our data demonstrated that caspase‐14 deficiency causes the imbalance of the skin‐resident bacterial communities.     

Oncogenic BRAF signalling increases Mcl‐1 expression in cutaneous metastatic melanoma

The Bcl‐2 family member Mcl‐1 is essential for melanoma survival; however, the influence of oncogenic BRAF signalling remains elusive. In this study, Mcl‐1 splice variant expression was determined in a panel of melanoma cell lines in relation to BRAF mutational status. Mcl‐1L mRNA expression was increased in melanoma cells compared with primary melanocytes with significantly increased mRNA and protein expression observed in BRAF^V600E mutant melanoma cells. Although no change in Mcl‐1S mRNA was observed, Mcl‐1S protein expression also increased in BRAF mutant melanoma cells. Additionally, while over‐expression of mutant BRAF^V600E increased both Mcl‐1L and Mcl‐1S expression, inhibition of hyperactive BRAF signalling resulted in decreased Mcl‐1L expression. These studies suggest that the regulation of Mcl‐1 expression by BRAF signalling is increased by oncogenic activation of BRAF, revealing a mechanism of apoptotic resistance which may be overcome by the use of more specifically targeted Mcl‐1 inhibitors.     

CD80CD86 deficiency disrupts regulatory CD4+FoxP3+T cell homoeostasis and induces autoimmune‐like alopecia

Alopecia areata (AA) is an autoimmune disease that results in spot baldness in humans. Adequate animal models for AA are currently lacking. The objective of this study was to elucidate the mechanism of autoimmune-like alopecia (ALA) in C57BL/6.CD80CD86-deficient (B6.CD80CD86^−/−) mice. Incidence and severity of alopecia were analysed in 58 B6.CD80CD86^−/− mice using histological examination, flow cytometry, multiplex enzyme-linked immunosorbent assay, quantitative RT-PCR and CD25 inhibition test. Both male and female B6.CD80CD86^−/− mice showed almost 100% incidence of hair loss at 40 weeks of age. Moreover, CD4+FoxP3+Treg (Treg) cell population in B6.CD80CD86^−/− mice was significantly lower than in B6 mice, which presumably underlined autoimmune reaction. Histologically, B6.CD80CD86^−/− mice showed CD4+ and CD8+ T-cell infiltration around terminal follicle region and exhibited hair follicle destruction in the anagen or catagen stage. Negative correlation between the number of CD4+FoxP3+ Tregs and ALA was confirmed by the CD25 depletion test in B6 mice, as follicle destruction was similar to that observed in B6.CD80CD86^−/− animals. CD80CD86 deficiency disrupted CD4+FoxP3+ Treg homoeostasis and prompted the development of ALA. We demonstrated that B6.CD80CD86^−/− mice might have several advantages as an ALA model, because they exhibited high incidence of disease phenotype and epipathogenesis similar to that observed in human AA.     

Oligosaccharide modification by N‐acetylglucosaminyltransferase‐V in macrophages are involved in pathogenesis of bleomycin‐induced scleroderma

Oligosaccharide modification by N‐acetylglucosaminyltransferase‐V (GnT‐V), which catalyses the formation of β1,6 GlcNAc (N‐acetylglucosamine) branches on N‐glycans, is associated with various pathologies, such as cancer metastasis, multiple sclerosis and liver fibrosis. In this study, we demonstrated the involvement of GnT‐V in the pathophysiology of scleroderma. High expression of GnT‐V was observed in infiltrating cells in skin section samples from systemic and localized patients with scleroderma. Most of the infiltrating cells were T cells and macrophages, most of which were CD163⁺ M2 macrophages. To determine the role of GnT‐V in scleroderma, we next investigated skin sclerosis in GnT‐V knockout (MGAT5^?/?) mice. Expression of GnT‐V was also elevated in bleomycin (BLM)‐injected sclerotic skin, and MGAT5^?/? mice were resistant to BLM‐induced skin sclerosis with reduced collagen type 1 α1 content, suggesting the biological significance of GnT‐V in skin sclerosis. Furthermore, the number of CD163⁺ M2 macrophages and CD3‐positive T cells in BLM‐induced skin sclerosis was significantly fewer in MGAT5^?/? mice. In bone marrow‐derived macrophages (BMDMs), IL‐4‐induced expressions of Fizz1 and Ym1 were significantly reduced in MGAT5^?/? mice‐derived BMDMs. Taken together, these results suggest the induction of GnT‐V in skin sclerosis progression is possibly dependent on increased numbers of M2 macrophages in the skin, which are important for tissue fibrosis and remodelling.     

The effects of protective occlusive gloves on stratum corneum barrier properties *

Data suggests that protection From gloves is paradoxically reduced became of effects of occlusion on the skin. The aim of this study was to characterize these effects on physical and functional properties of stratum corneum. Volunteer trials were conducted using patches of polyvinyl chloride (PVC) glove material on the skin. Impairment of barrier function -was assessed by measuring transepidermal water loss (TEWL). Hydration and water sorption-desorption was assessed using skin conductance. The major finding was a short-term impairment of barrier function, measured as an increase in TEWL of 1.7 gn ^?2 h ^?1 (95% C.I. 0.4 to 2.6 gn ^?2, h ^?1, p < 0.01) Temporary increases in hydration and water sorption were also observed. On this basis, the effects of wearing PVC gloves over 2 days on stratum corneum barrier properties on the dorsum of the hand were studied. TEWL measurements remained elevated by 1.5 gn ^?2 h ^?1 the day after occlude glove removal (95% C.I 0.2 to 2.8 gn ^?2 h ^?1, p < 0.01), indicating a possible cumulative effect. In conclusion, our studies demonstrate a potential hazard resulting from the repeated use of protective gloves.     

Blond hair removal using ELOS systems

Objective: The aim of this study was to test blond hair removal using the ELOS system, which is optical energy and radio‐frequency combined. Methods: Seventeen patients with blond hair were randomly selected from the Department of Lasertherapy, Medical Centre Maastricht, The Netherlands. The mean age of the patients was 57.4 years. The mean energy used per patient was 23.2?J/cm² and the mean radio‐frequency was 18.6?J/cm². Results: A mean hair reduction of 57.4% was obtained with a mean of 8.5 treatments. There was a trend found between hair removal and the number of treatments. No correlation was found between the percentage of hair removal and age. Furthermore, there was no correlation between hair removal and the device's technical data. No major side effects were observed postoperatively. Conclusions: This study showed that ELOS can effectively be used for blond hair reduction.     

Histological hair removal study by ruby or alexandrite laser with comparative study on the effects of wavelength and fluence

BACKGROUND: Several different laser systems are currently used to remove unwanted hairs. In this study, we studied follicular changes following hair removal with ruby or alexandrite lasers at different fluences.

METHODS: Unwanted hairs were treated with a ruby laser (Chromos 694, ICN PhotonIcs, UK) at 10, 14 or 18?J/cm² or with an alexandrite laser (LPIR, Cynosure, USA) at 11, 14 or 17?J/cm². A 3?mm skin punch biopsy was taken immediately after each laser exposure and also 1 month later. Specimens were stained for histological observation. They were observed using immunohistochemistry with antibodies recognizing factor VIII related antigen or PCNA, and also by the TUNEL method. Similarly, electron microscopic observation was examined.

RESULTS: Immediately after the laser exposure, moderate follicular damage was observed following treatment with either type of laser. One month later, cystic formation of hair follicles and foreign body giant cells were observed in skin treated with either type of laser. A similar fluence with either laser treatment resulted in similar histological changes.

CONCLUSION: In this study, the histological changes following treatment with a ruby or an alexandrite laser at the same fluence are similar.     

Melanin and facial skin fluorescence as markers of yellowish discoloration with aging

Background: Although one clinical sign of aging and/or photoaging is a yellowish discoloration of the facial skin, little is known about the cause of this change. In addition to the increase in the epidermal melanin content, it has been suggested that advanced glycation end products (AGEs), which are known to accumulate in photoaged skin, may affect this discoloration. Aim: The objective of this pilot study was to non‐invasively investigate the roles of melanin and AGEs in this yellowish discoloration of the facial skin. Methods: We examined the spectral reflectance at the cheek in 40 healthy Japanese women of various ages (mean age, 38.1 years) using a reflectance spectrophotometer and a spectrofluorimeter. The degree of yellowish tint was evaluated in terms of b^*. The amount of melanin in the skin was evaluated by calculating the melanin index (MI) A₆₄₀–A₆₇₀ [A_λ: log₁₀ (1/reflectance) at a wavelength of λ]. The amount of AGEs was roughly evaluated using the AGEs index, which is thought to linearly correlate with the amount of intrinsic fluorescence markers irrespective of the concentration of melanin and is defined as follows: AGEs index=I₅/SQR (I₁×I₂). In this equation, the intensities of reflectance are I₁ at an excitation wavelength of 335 nm, I₂ at an emission wavelength of 390 nm and I₅ at 390 nm under an excitation wavelength of 335 nm. Results: Both b^* and the AGEs index were significantly correlated with subject age (r=0.34, P<0.05 and r=0.68, P<0.0001, respectively). Significant correlations were also observed between MI and b^* (r=0.63, P<0.0001) and between the AGEs index and b^* (r=0.53, P<0.0005). However, no significant correlations were seen between MI and the AGEs index. Conclusion: The AGEs index does not appear to be influenced by the amount of melanin and may be utilized as an indicator of the amount of AGEs in the skin. AGEs are likely to play a role in the yellowish discoloration of skin with aging.     

The predominant drug-specific T-cell population may switch from cytotoxic T cells to regulatory T cells during the course of anticonvulsant-induced hypersensitivity

Background

Delayed hypersensitivity is responsible for severe cutaneous adverse drug reactions (cADRs), especially in Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis, and drug-induced hypersensitivity syndrome (DIHS) (also known as drug rash with eosinophilia and systemic symptoms [DRESS] syndrome). The drug-induced lymphocyte stimulation test (DLST), or lymphocyte transformation test (LTT), is used to identify the culprit drug in severe cADR cases.

Objective

The aim of this study was to examine the immune reactions in cADR patients through the identification of the drug-specific proliferating cells by flow cytometric DLST (FCM-DLST).

Methods

The peripheral blood mononuclear cells of 16 anticonvulsant-induced cADR patients were investigated by conventional DLST and a FCM-DLST protocol in which CFSE dilution and BrdU incorporation were combined. FCM-DLST allowed for the identification of the drug-specific proliferating cells in six cases. Three of these cases were DIHS cases, whereas there was one case of SJS, one case of maculopapular rash (MP), and one case of erythema multiforme (EM) among the six cases.

Results

In FCM-DLST, drug-specific proliferating T cells were detected as CFSE^low BrdU^high cells. These cells corresponded to the cells incorporating ³H-thymidine in conventional DLST. Although CD4⁺ T-cell proliferation dominated the observed proliferation in most of the cases (in the recovery stage of the three DIHS cases, the MP case, and the EM case), drug-specific CD8⁺ cytotoxic T lymphocytes (CTLs) were detected, especially in the acute stages of the SJS case and one of the DIHS cases. There was a dramatic switch in the predominant drug-specific proliferating T-cell population in the course of one of the cases of DIHS in which CD8⁺ CTLs were predominant initially, whereas CD4⁺ T cells were predominant later. Moreover, drug-specific CD4⁺ CD25⁺ Foxp3⁺ regulatory T cells (Tregs) proliferated during the recovery stage in one DIHS case.

Conclusions

FCM-DLST revealed that the cell proliferation detected by conventional DLST is a heterogeneous proliferation of both CD8⁺ CTLs and CD4⁺ T cells that likely includes Tregs. However, the number of cADR cases in this study was limited, which limits the conclusions that can be drawn from it.     

Developmental expression of C3 receptor on murine epidermal Langerhans cells during ontogeny

Summary The developmental expression of C3 receptor, an important surface marker of murine epidermal Langerhans cells (LCs), was quantitatively studied using an immunohistochemical technique on epidermal sheets and then compared with developmental expression of Ia antigen and membrane ATPase. Anti-Mac-1 monoclonal antibody associated with CR3 was used for detecting C3 receptor and proved positive for LCs by immunoelectron microscopy. Mac-1 positive (Mac-1⁺) cells showed quite a different distribution from those of ATPase⁺ and Ia⁺ cells. Almost the same number of Mac-1⁺ and ATPase⁺ cells were present during the embryonic period. The number of Mac-1⁺ cells gradually decreased from day 1 to day 5 of postnatal life, after which they increased again. Using the doublelabeling technique on epidermal sheets at day 1 of postnatal life, it was shown that Ia⁺ cells possessed membrane ATPase activity and some Mac-1⁺ cells expressed Ia antigen. On days 4 and 7 of postnatal life all Mac-1⁺ cells expressed Ia antigen. These findings suggest that Mac-1 antigen observed during the embryonic period gradually fades after birth and is re-expressed after day 5 of postnatal life.