red blood cells, leukocyte or white blood cells, are the cells of the immune system, infection. medical concept of human

abstract anatomy artery background bcell biology blood body cancer cell circulatory disease erythrocyte flow health hemoglobin human illness immune immunity immunology infection leukocyte life macro magnification medical medicine micro microbiology microscope microscopic organic organism plasma platelets red research science scientific sick sickness system vascular vein vessel virus white