Final answer:
In the immune system, mononuclear cells like monocytes and lymphocytes are involved in the adaptive immune response, while neutrophils, a type of granulocyte, engage in immediate innate immune responses to infections.
Step-by-step explanation:
In the context of the immune response and the cells involved, when a fluid contains mostly mononuclear cells, it indicates an immune reaction where agranulocytes like lymphocytes and monocytes are predominant. These cells are important in the adaptive immune response as well as in the differentiation into other cell types like macrophages and dendritic cells that respond to infections or injuries. On the other hand, when neutrophils predominate, it is indicative of an earlier, more immediate response to infection or injury. Neutrophils are a type of granulocyte and are known for their phagocytic capabilities and quick response to inflammation, making them critical in the innate immune response.
Neutrophils are the most common leukocytes and are characterized by fine, light lilac granules and a lobed nucleus that increases in lobes as the cell ages. Monocytes, when they leave the bloodstream and enter tissues, can differentiate into macrophages or dendritic cells. Abnormally high counts of monocytes are associated with various infections and chronic diseases, while fluctuations in neutrophil counts can indicate different stages or types of inflammation and immune responses.