The basis of humoral immunity is the functioning of biologically active substances present in blood plasma, lymph, tissue fluid (for example, antibodies, lysozyme, interferons, proteins of the complement system).
In the reactions of cellular immunity, the protective function is performed directly by cells (leukocytes), which make direct contact with a foreign object and destroy it (for example, destruction of tumor cells by T-killers, phagocytosis).
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.