Further observations on the role of the MHC genes and certain hearing disorders.

The pathogenetic mechanism of many hearing disorders have not been fully defined. Studies of certain hearing disorders in man have suggested a role for the major histocompatibility complex (MHC)-encoded genes in disease pathogenesis. In a cohort of unrelated patients with Meniere's Disease, otosclerosis and strial presbycusis as well as other types of sensorineural hearing losses, we have identified an extended MHC haplotype common to the majority of these patients, supporting a hypothesis that a gene(s) within the MHC domain may confer susceptibility to these hearing ailments. In addition, a preliminary study of 27 individuals with various hearing maladies, a striking finding is that 44% of the patients express the following extended MHC haplotype in contrast to only 7% of the general population: DQw2-DR3-C4BSf-C4A0-G11:15-Bf:0.4-C2a-HSP70:7.5-TNF a5-B8-Cw7-A1. The expression of this haplotype by subsets of patients with hearing loss is significant in comparison to regional and international controls.

Complement components and receptors: deficiencies and disease associations.

The complement system, accessory to many immunological functions, consists of a number of interdependent components and receptors. Numerous in vitro approaches have elucidated the biological role of these components and receptors. However, it is the in vivo "natural" experiments that underscore their importance. The phagocytosis and subsequent digestion of pyogenic bacteria is significantly enhanced by the fixation of the third complement component to the bacterial cell wall. Equally important is the intact expression of a receptor (CR3) for the C3b cleavage fragment. Breakdown in this ligand-receptor interaction due to either C3 or CR3 deficiency leads to pyogenic infection. Interestingly, C3-deficient individuals do not demonstrate leukocytic infiltration at the site of infection. Undoubtedly, this is due to the lack of C5 convertase and failure to produce C5a. CR3-deficient individuals, on the other hand, do demonstrate leukocytosis since the third complement component is functional. C3 deficiency is not necessarily a primary lesion and may be secondary to factor I deficiency. In this case, the C3b fragment, along with factor B, acts as a C3 convertase. Inefficient inactivation of C3b, due to factor I deficiency, leads to the uncontrolled consumption of the third component, resulting in C3 deprivation. It appears that phagocytosis by neutrophils and monocytes followed by enzyme-interaction is not sufficient for destruction of the Neisseria organisms. In addition to this leukocyte activity, an intact membrane attack complex, composed of the late complement components C5, 6, 7, 8, and 9, is required for the lysis of these bacteria. This is supported by findings that individuals deficient in late components are highly susceptible to systemic Neisseria infections. Diseases of an autoimmune nature are frequently associated with a deficiency of one of the early complement components C1, C2, or C4 and a deficiency of erythrocytic CR1 receptors as well. This may suggest that proper interaction between a complement fragment of the immune complex with the complement receptor expressed on the erythrocyte is important for proper management and clearance of the complex. Deficiency of the early complement components would prevent the activation of C3 and the fixation of a resulting C3 cleavage product. In this case, erythrocytes would be unable to participate in the transport of the immune complex to the reticuloendothelial system. Instead, tissue deposition of the complex would occur more readily, contributing to the pathologic process. Provided that the early complement cascade were intact, deficiency of erythrocytic CR1 receptors would contribute to the pathologic response for the same reason.(ABSTRACT TRUNCATED AT 400 WORDS)

Evaluation of HLA-DR typing by ethidium bromide fluorescence.

Sixty individuals were typed for D-related human leukocyte antigens (HLA-DR) using two methods: the standard eosin exclusion method and a recently described one-color ethidium bromide technique. As a result, 88 of the 90 DR antigens detected by the standard technique were also detected by one-color fluorescence (sensitivity = 97.8 percent). However, of the 99 DR antigens identified by ethidium bromide fluorescence, 11 were left undetected by eosin exclusion (sensitivity = 88.9 percent). The one-color ethidium bromide fluorescence technique, although originally intended to conserve technical time, demonstrated an additional advantage in our laboratory. The enhanced sensitivity of the procedure may help in the identification of previously undetected DR antigens.

Cellular changes and antitumor responses in the plasmacytoma-bearing mouse following cyclophosphamide treatment.

Mice bearing the immunosuppressive plasmacytoma TEPC-183 exhibit a marked splenic hyperplasia. We have characterized these tumor-reactive splenocytes on the basis of cell surface marker expression, nonspecific esterase activity, and morphology. Although splenocyte numbers increased progressively throughout tumor growth, B- and T-lymphocytes, as defined by surface immunoglobulin and Thy-1 antigen expression, respectively, did not increase significantly. Fourteen days after tumor implantation, T-lymphocytes decreased from 70 million to 50 million per spleen. However, cells expressing Mac-1 antigen or nonspecific esterase activity increased from 10 to 65 million. This constituted a 6-fold increase in splenic macrophages. Further studies utilizing the expression of PC.2 antigen in conjunction with morphological examination indicated that metastatic TEPC-183 cells comprise approximately 5% of the tumor-host splenocyte population 14 days after implantation. Ablation of plasmacytoma by cyclophosphamide inhibited the tumor-associated splenocytosis and led to an increase in splenic T-cells (from 70 to 120 million). In addition, macrophage numbers returned to normal. This study also assessed the ability of splenocytes from animals with either actively growing tumors or those from cyclophosphamide-treated tumor-bearing mice to mediate an antitumor response. Splenocytes, when assessed 1 wk following tumor ablation by cyclophosphamide, demonstrated antitumor activity in Winn neutralization assays. This activity was not detectable in splenocytes from animals with progressively growing tumors. Additional studies revealed that the cell population involved in the antitumor effect was glass nonadherent, nylon-wool nonadherent, and expressed Thy-1 antigen. These observations were consistent with the expansion of the splenic T-lymphocyte population following cyclophosphamide treatment. However, the immune response directed against primary TEPC-183 tumor cells was not inhibitory to metastatic tumor cells.