useful to be able to refer to pseudohyphae and hyphae collectively and we will use the term ‘filamentous’ for this purpose [13]. However, hyphae are narrower than pseudohyphal cells (2 mm) and have parallel walls with no obvious constriction at the site of septation [13]. Germ tubes are the initial projections observed when C. albicans switches from yeast form to hyphal growth [16]. Growth is polarized in C. albicans hypha, with continu- ous apical growth throughout the cell cycle and parallel cell walls at the septal junctions. In contrast, the growth of pseudohypha and blastophores is only limited to the apical tip during the initial part of the cell cycle [17]. Pseudohypha can also be distinguished from true hypha on the basis of their morphological index which quanti-fies the dimensions of cell compartments. Alternatively they can be distinguished on the basis of the positions of their septal junctions. These lie at the bud neck for pseu- dohypha, and within the germ tube for emerging hypha [13]. Hyphae, pseudohyphae and yeast differ from each other in the rate and order of cell cycle events [18].
Morphogenesis is interrelated to the pathogenesis of C. albicans. Adherence has been shown to play critical role in the pathogenesis of infections. Germ tubes, that are short hyphal elements, are important in the adherence of organism to the host epithelium [19-21]. Hypha of C. albicans are also important for tissue destruction and host invasion [22]. The yeast form of C. albicans also have virulence attribute and is thought to promote dis-semination within the blood stream and establishment of infection at distant sites [8,13,23,24]. Several researchers have investigated that hyphal form is more virulent than yeast form [25-27]. The principal determinant in the de- velopment of disease is the ability of C. albicans to switch between yeast and hyphal forms rather than the individual morphologies [28].
There are various host defense mechanisms against C. albicans infections which mainly include phagocytosis of fungal cells by the cells of innate immune system (ma- crophages and neutrophils). Phagocytic clearance of fun- gal pathogens may be considered to consist of four dis- tinct stages; 1) accumulation of phagocytes at the site where fungal cells are located; 2) recognition of fungal pathogen by specific receptors [29]; 3) engulfment of fungal cells bound to the phagocyte cell membrane, and 4) processing of engulfed cells within phagocytes by fusion with lysosomal vesicles to form the phagoly- sosome [30]. Yeast forms of C. albicans cells are more effectively engulfed by macrophages as compared to hyphal forms. Hyphal cells are engulfed at a slower rate than yeast cells. The delayed engulfment may result in the detachment of fungal cell [31]. Furthermore, the yeast-form of C. albicans cells that are phagocytosed by macrophages switches to the hyphal form and escape the macrophages. This switching is particularly important in escaping the defense mechanism of the host [7].