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Journal of the Anatomical Society of India

Apposition of Langerhans cells and lymphocytes in Human tonsillar epithelium: An Ultrastructural study

Author(s): I. Indrasingh

Vol. 55, No. 2 (2006-07 - 2006-12)

I. Indrasingh
Christian Medical College, Vellore, India.

Abstract:

Langerhans cells are known to play an important role in cutaneous immune responses. The tonsils likewise have been regarded as lymphoid tissue performing critical functions in the immune system. Earlier we have demonstrated the presence of Langerhans cells in the human tonsillar epithelium by ultra structural study. It is well established that Langerhans cells (LC) is an accessory cell of the immune system which is able to bind and present antigen to T – lymphocytes for triggering an immune response. Morphological evidence for this function is provided by the close apposition of lymphocytes and Langerhans cell. Having identified the Langerhans cells in the human tonsillar epithelium, the present study was carried out to look for the apposition of Langerhans cells and lymphocytes using conventional electron microscopy. Langerhans cells with typical Birbeck granules and their close contact with the intraepithelial lymphocytes were seen in the human tonsillar epithelium. In some places their dendritic process showed close apposition with the lymphocytes. The apposition of tonsillar epithelial Langerhans cells with the lymphocytes suggests a functional role in the generation of local immune responses analogues to skin.

Key words: Langerhans cells, Ultrastructure, Apposition of lymphocytes, Human palatine tonsil

Introduction:

The dendritic Langerhans cells were first observed in the skin in 1868 by Paul Langerhans. Nearly a century later, Birbeck et al. (1961) demonstrated the characteristic rod- like granules in the cytoplasm of the Langerhans cells ultrastructurally. Langerhans cells belonging to the system of antigen presenting cells, binding the antigen that penetrates the epidermis and presenting it to T-lymphocytes, which generate an immune response, Silberberg (1973), Stingl et al. (1978), Braathen et al. (1984), and Katz et al. (1985).

Morphological evidence for this function is provided by the close apposition of lymphocyes and Langerhans cells that occurs in the cellular hypersensitivity, e.g., contact dermatitis, Silberberg et al. (1975), as well as in the neoplastic process, Caorsi & Figueroa (1984). Concha et al. (1988) reported three different types of contact zones between the Langerhans cells and lymphocytes in the experimental contact dermatitis in mice and human cervical carcinoma and mycosis fungoides. Pope et al. ( 1997) suggested that mucosal DC-T cell environment may be the site of immunodeficiency virus replication

The palatine tonsils play an important role in immunologic surveillance and resistance to infection in upper aero digestive tract. Our earlier study revealed the presence of Langerhans cells (LC) in the human tonsillar epithelium, Chandi et al. (1988, 1989), and Indrasingh et al. (1999, 2000, 2002) The determination of the interaction between the antigen presenting Langerhans cells and immunocompetent cells (Tlymphocytes) is of much more importance to clarify the cellular interactions in the palatine tonsils. So in the present study our aim was to demonstrate the apposition of Langerhans cells and lymphocytes in Human tonsillar epithelium by using the conventional electron microscopy.

Materials and methods:

Tonsillar tissue collected from four patients undergoing tonsillectomy for recurrent tonsillitis were finely divided under a dissecting microscope and fixed in phosphate buffered glutaraldehyde-formalin mixture at pH 7.2-7.4 for 4 hours. The material was then washed in phosphate buffer, post fixed in 1% Osmic acid for 90 minutes, washed again in phosphate buffer, dehydrated in graded alcohols, cleared in propylene oxide and embedded in araldite. Ultra thin sections were cut with a glass knife and viewed under a Philips E.M 201 at 60 Kv.

Results:

The Langerhans cells were identified in the human tonsillar epithelium, as pale staining cells, devoid of tonofilaments, desmosomes, their nuclei were of deeply indented. Their cytoplasm contains free ribosomes, mitochondria, electron dense lysosome – like structures, and Golgi bodies. Birbeck granules were seen in the cytoplasm, which in sectional profile, resembled horse-shoes, rod and tennis – racket shaped (Fig.1). It also shows the close contact between the Langerhans cell and the two lymphocytes in the surface epithelium of the human palatine tonsil. In few places the dendritic process of the Langerhans cell was in apposition with the lymphocytes (Fig.2).

Fig. 1: Apposition of Langerhans cell and the two lymphocytes (L) in the surface epithelium of Tonsil. Arrow shows the Birbeck granules which are tennis racket and horse-shaped (X, 9184).

Fig. 2: A Langerhans cell with single dendritic process, the tip of the process is in apposition with the lymphocyte (L). Arrow shows the rod shaped Birbeck granules (X, 6457).

Discussion:

There were very few reports regarding the demonstration of Langerhans cells in the human tonsillar epithelium. Mausle et al. (1971) reported the evidence of Langerhans cells in the epithelium of human tonsil by Zinc Iodide Osmium method. Weinberg et al. (1987) demonstrated dendritic cells in human tonsillar epithelium by their capacity to bind the lectin, peanut agglutinin, and their reaction with variety of monoclonal antibodies. From our earlier study, we found that Zinc Iodide-Osmium dendritic cells were not distributed uniformly or compactly in the tonsillar epithelium, Chandi et al. (1988). We also demonstrated the Langerhans cell with Birbeck granules ultrastructurally in the surface epithelium as well as in the crypt epithelium of the human tonsil, Chandi et al. (1989), Inbam Indrasingh (2000), Indrasingh et al. (2002). Perry (1994) could not demonstrate typical Langerhans cell in the crypt epithelium of human palatine tonsil. Langerhans cells in the epithelium of human palatine tonsil during the prenatal development were reported by Holibka (1998).

Having identified the presence of Langerhans cells in the human palatine tonsil, in the present study, we have demonstrated the morphological evidence for their function as antigen presenting cells, mainly the close contact between the Langerhans cell and lymphocytes (Fig.1 and 2). This apposition of lymphocytes and the Langerhans cells have been observed in some human pathological processes in which these cells are involved, Rowden et al. (1979), and Caorsi et al. (1982).. Silberberg (1975) showed the close apposition of lymphocytes to LC in cellular hyper sensitivity. Ozbilgin et al. (2004) studied the antigen presenting cells in the hypertrophy pharyngeal tonsils of the children and found that the pharyngeal tonsils contained several types of active antigen presenting cells, only dendrite cells were in close contact with immunocompetent cells and other antigen presenting cells .

Okato et al. (1989) demonstrated the sites of interaction between the antigen presenting cells (dendritic cells, macrophages) and the lymphocytes in the human palatine tonsil by pre-embedding immunoelectron microscopy and acid-phosphatase histochemistry. But in this study we have used the conventional electron microscopy method to demonstrate the close contact between the Langerhans cell and the lymphocytes. The ultra structural demonstration of close contact between the Langerhans cells with the lymphocytes in the tonsillar epithelial microenvironment, like skin, suggests a functional relationship in the generation of local immune responses.

Acknowledgement:

We acknowledge with gratitude the financial support provided for this study by the Fluid Research committee of the Christian Medical College and the Technical assistance given by Mr. Swamy Nathan. We are also grateful to the Welcome Research unit of this Institution for permitting the use of their Electron Microscope.

References:

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