Caption

False-colour scanning electron micrograph (SEM) of a cultured lymphocyte phagocytosing (engulfing) a yeast cell. At right, the lymphocyte white blood cell (blue) is extending towards the yeast spore (yellow) with pseudopodia projections of its cyto- plasm. The yeast cell will finally be swallowed up and digested. Lymphocytes circulate in the blood and play an essential role in the immune response, collecting at sites of infection to repel foreign invaders. Although lymphocytes move by amoeboid locomotion, most are non-phagocytic and instead attack invaders with enzymes. The yeast cell here is similar to the fungus that causes candidiasis (thrush) in humans. Magnification: unknown.