Oral Oncol, EurJ Cancer, Vol. 298, No. 3, PP. 181-185, 1993 096C1955/ 93 S6.00f 0.00 hinted In Great Britain Pergnmon Press Ltd zyxwvutsr Immunological Phenomena in Human Oral Carcinoma in India zyxwvutsrqponmlkjihgfedcbaZYXW T. Vijayakumar, K.R. Shanavas and D.M. Vasudevan zyxwvutsrqponmlkjihgfe INTRODUCTION ORAL CANCER zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA is one zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA of the 10 most common cancers in the world, and in countries like India, Pakistan, Bangladesh and Sri Lanka it is the most common cancer. Hospital-based registries in India reveal that oral cancer accounts for about 30-40% of all malignancies in the country [I]. The prevalence of oral premalignant lesions, such as leukoplakia and submuc- ous fibrosis, has also been found to be high in this country. The aetiology of these high incidences of oral premalignant and malignant lesions is not fully understood. Chewing and smoking of tobacco, and consumption of alcohol have been reported to be associated with oral premalignant and malig- nant lesions [2-41. Studies have also revealed an association of the herpes group of viruses with oral cancer [5-91. Despite marked improvements in various therapeutic modalities, the rate of 5-year survival among oral cancer patients is still low. Throughout the world extensive investigations have been undertaken during the past two decades, on the various aspects of oral cancer. Immunology of oral cancer has been a subject of active research. This article aims to review the major immunological studies undertaken so far in India. CELL MEDIATED IMMUNITY It is now generally accepted that there are immunological derangements in cancer patients, and alterations in the cell- mediated immunity (CMI) in malignancy have become appar- ent in several studies [lo, 1 I]. The assessment of CM1 is, therefore, believed to be useful in the diagnosis and/ or prog- nosis, as well as in the treatment of cancer. The failure of immune surveillance has been reported to be an important factor in the development and progression of cancer [ 121. Tumour specific antigens may be present both on the surface as well as in the interior of tumour cells. Specific antibodies to the neoantigens may bind to the surface antigens leading to complement fixation and subsequent lysis of the tumour cells. Immunologically specific cytotoxic T-cells may bind to surface antigens and destroy the tumour cells or inhibit their growth. Studies on animal models have revealed the blocking of antigen-recognition sites on lymphocytes by circulating tumour specific antigens. Reports on such blocking factors in human cancers are rather rare [ 13, 141. zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Lymphocytes Alteration of the surface characteristics of lymphocytes can lead to changes in their circulation pattern inside the body. Correspondence to T. Vijayaknmar. T. Vijayakumar is at the Deparnnent of Science and Technology, Trivandrum, Kerala, India 695 037; and K.R. Shanavas and D.M. Vasudevan are at the Department of Biochemistry, Medical College, Trichur, India 680 596. Received 22 July 1992; manuscript provisionally accepted 25 Aug. 1992; revised manuscript received 5 Nov. 1992. Changes in the distribution pattern of lymphocytes subjected to alterations of surface characters by neuraminidase treat- ment [15] or by anti-lymphocyte serum treatment [16] have been demonstrated. Vijayakumar [ 171 undertook a study to evaluate the altera- tions in the surface characteristics of lymphocytes from oral cancer patients in India, by noting the homing pattern of the lymphocytes in mice. Lymphocytes from oral cancer patients and normal subjects were labelled with radioactive chromium and injected into the experimental animals. The radioactivity in the liver and spleen of the mice was measured subsequently to understand the homing pattern of the lymphocytes. Com- pared to normal, the lymphocytes from oral cancer patients showed a drastic change in homing pattern. This study sug- gested that the surface characteristics of the lymphocytes in oral cancer patients are altered possibly due to the presence of blocking factors (antigen, antibody or antigen-antibody complexes). Incubation of the lymphocytes prior to injection into mice resulted in regaining of the normal homing pattern, possibly due to the removal of blocking factors. Balaram and Vasudevan [18] quantitated total lympho- cytes, B-cells and the T-lymphocyte subsets, TG cells (IgG Fc receptor bearing T-cells) and TrV!cells (IgM Fc receptor bear- ing T-cells), in the peripheral blood of oral cancer patients and normal subjects. A significant increase in the number and proportion of TG cells and a significant reduction in the TM cells were noted in the cancer patients. The increase in TG subset was obvious in the early stages of the disease, whereas the reduction in T, subset was evident only in the advanced stages. Vijayakumar and Vasudevan [19] used enumeration of T lymphocytes, by rosette formation with sheep erythrocytes (SRBC), as a parameter to assess CM1 in oral cancer patients. In the study, total rosette forming cells (TRFC-T cells form- ing rosettes with SRBC at low temperature on prolonged incu- bation) and high affinity rosette forming cells (HARFC-T- cells forming rosettes at 29°C with fewer SRBC) were enumerated. No changes were observed in TRPC in the patients. On the other hand, HARFC were found to be decreased in the cancer patients, and this decrease became more pronounced with progression of clinical stage. Further, normal HARFC levels were observed in the patients with total tumour remission, while it remained depressed in patients with residual tumour after treatment. It was, therefore, con- cluded that the enumeration of HARFC may be a simple, reliable and a relatively less expensive method to assess CM1 in cancer patients. In a later study, Rajendran et al. [20] reported depression of HARFC in patients with oral sub- mucous fibrosis. Pillai et al. [21] f ound reduced total lymphocyte counts in oral cancer patients. This study also revealed a significant increase in the proportion and count of B-lymphocytes in premalignant lesions. Reduction in the absolute number and 181