Answer:
The observed image will not be sharp
Explanation:
When 100x microscope objective lens is being used, light refraction in the air is enough high to produce image alterations. Image distortions can be minimized by immersion oil because this liquid has a higher refractive index than air. However, light refraction is not usually noticeable when using 4x, 10x and 40x objective lenses. Moreover, this image will not be sharp after putting oil on the slide and going back to the 40x objective, it is for that reason that the 40x is called 'high dry' lens. In consequence, it is required to clean the immersion oil off the 40x objective. In general, it is required to to remove the oil and refocus off the slide and lens immediately after oil immersion (it can be done by using an oil-soluble solvent).
Answer:
Helper T cells are arguably the most important cells in adaptive immunity, as they are required for almost all adaptive immune responses. They not only help activate B cells to secrete antibodies and macrophages to destroy ingested microbes, but they also help activate cytotoxic T cells to kill infected target cells.
Explanation:
Helper T cells become activated when they are presented with peptide antigens by MHC class II molecules, which are expressed on the surface of antigen-presenting cells (APCs). Once activated, they divide rapidly and secrete cytokines that regulate or assist the immune response.
