**2.1 Host immune response**

The cell surface receptors on *C. albicans* initiate adhesive interactions and invade the host cell using a series of proteins including adhesins and invasins. These immunodominant factors would trigger and stimulate a complex interplay of natural and adaptive immunity, posing interesting immunological response to the host. Cell-mediated (T cells) and innate immunity (macrophages, neutrophils and natural killer cells) are considered to be the most important line of defense against candidiasis [4] as they are recruited into the site of infection to exert protective effects. These include phagocytosis and antigen presentation, opsonization and production of chemicals for effective killing of the microbial cells. It must be emphasized therefore, that these responses comprise of different arms of the immune system (innate, cell-mediated and antibody-mediated) as shown in **Figure 1**.

### *2.1.1 Innate immunity*

White blood cells are produced and derived from multi-potent cells in the bone marrow known as hematopoietic stem cells and are found throughout the body, including the blood and lymphatic system [8]. Five individual types of white blood cells namely neutrophil, monocytes, lymphocytes, basophils, eosinophils [9] are involved in sustaining immunity [10].

Innate immune response is the dominant protective mechanism against disseminated candidiasis [11] and host defense against fungal infection depends on elimination of the fungi by phagocytic cells of the innate immune system, especially neutrophils and macrophages [12] at the initiation of infection before other immune cells are mobilized. Therefore, white blood cells are used to assess the working condition of body's immune system, to determine an active or chronic infection, identify the type of infection and also point to an allergic response or inflammation in the body [9].

Hence, quantitative and qualitative abnormalities of these immune cells are indications to different physiological conditions and particularly neutrophils and monocytes are associated with systemic candidiasis.
