Final answer:
The term 'basket cell' is not standard for describing immune cells, but the described features suggest the term likely refers to lymphocytes, specifically NK cells, which are large with a prominent nucleus that stains purple. Lymphocytes are essential for the immune response and can vary in size.
Step-by-step explanation:
A basket cell is not a standard term frequently used in biology, particularly in the context provided by the question. It seems there may be confusion with a term more commonly used within neuroscience to describe a type of inhibitory interneuron found in the brain's cerebellum that is responsible for synaptic modulation. However, the information provided about spherical cells with large nuclei that stain purple seems to describe lymphocytes, a type of white blood cell. Among lymphocytes, Natural Killer (NK) cells, as well as B and T cells, fit the description of having a large nucleus occupying much of the cell's volume and staining darkly when assessed microscopically using Wright stain. Lymphocytes arise from lymphoid stem cells, develop in the bone marrow, and are crucial for the immune response.
Regarding the size, lymphocytes typically range from 6-9 μm for smaller cells, which have a larger nucleus-to-cytoplasm ratio creating a halo effect, to larger ones ranging from 10-14 μm, and sometimes even 14-17 μm. NK cells are a part of the innate immune system and can destroy virus-infected cells or cancerous cells by recognizing altered MHC class I molecules on their surfaces.