Monoclonal and polyclonal antisera

The extensive application of the hybridoma technology for tissue phenotyping has demonstrated in the last decade that a number of heterodimeric molecules consisting of noncovalently associated α and β subunits (Hynes, 1992), named integrins, play a major role in cell-to-cell and cellto-interstitium interactions as well as in cell trafficking (Hemler, 1990; Albelda and Buck, 1990). The structural and functional properties of these receptors molecules, which are either selective or promiscuous in their ligand specificity, have been so far mainly analyzed in in vitro models. Thus detailed knowledge of their tissue distribution is of major interest in order to define their roles in embryonic development, tissue architecture and repair as well as in neoplastic transformation. In this context the VLA6 (Sonnenberg et al., 1986) integrin, which is formed by the non-covalent association of α6 and β1 chains, is of particular interest, since it represents a non-promiscuous receptor for the basement membrane glycoprotein laminin (Sonnenberg et al., 1988b). However, the α6 chain can alternatively associate with a different β chain to form the α6/β4 heterodimer (Sonnenberg et al., 1988a; Hemler et al., 1989; Kajiji et al., 1989), whose receptor activity has not been fully characterized. Although double determinant radioassays have provided an overall estimate of the α6/β4 complex distribution in human tissues (Falcioni et al., 1988), no detailed analysis of its cellular localization is available. To investigate this issue we have performed the present immunohistochemical study. Data to be presented indicate that, as described in rodents (Sonnenberg et al., 1990a), α6/β4 is in most instances coexpressed with α6/β1, with a cellular distribution strongly polarized towards the basement membrane.