The antibodies of the humoral immune system act

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The antibodies of the humoral immune system act against extracellular agents, such as toxins or bacteria, but are not active in the intracellular space and cannot fight viruses efficiently. In case of viral infection (and also of cancerous or precancerous cells), the immune attack is carried out by the cellular immune system, through which T and NK (natural killers) lymphocytes destroy specific cells and viruses. 19. How does the cellular immune response take place1? The lymphocytes that participate in the cellular immune response are T lymphocytes. T lymphocytes can be divided into three main types: cytotoxic T lymphocytes (cytotoxic T cell), helper T lymphocytes (helper cell) and suppressor T lymphocytes. Cytotoxic cells are the effectors of the system, meaning that they directly attack other cells recognized as foreign (for example, fungi cells, cells infected by viruses,
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neoplastic cells, graft cells, etc.). Helper cells and suppressor T lymphocytes act as regulators of the system by releasing substances that respectively stimulate and inhibit the immune action of T and B lymphocytes. After the primary immune response, memory T lymphocytes also remain in circulation to provide a faster and more effective reaction in the case of future infections. The Immune System Review - Image Diversity: T cells 20. What are the antigen-presenting cells of the immune system? The antigen-presenting cells of the immune system, also known as APC cells, are cells that carry out phagocytosis and the digestion of foreign (to the body) microorganisms, later exposing the antigens derived from these microorganisms on the outer side of their plasma membrane. These processed antigens are then recognized by lymphocytes, which activate the immune response. Several types of cells, such as macrophages, can act as antigen-presenting cells. The Immune System Review - Image Diversity: antigen-presenting cells Active and Passive Immunization 21. What are passive and active immunization? What is the difference between these types of immunization
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in terms of the duration of their protection? Active immunization is that in when an antigen penetrates the body, triggering the primary immune response and the production of memory lymphocytes and antibodies, which then provide a faster and more effective immune defense during future infections by the same antigen. Passive immunization is when immunoglobulins against an antigen are injected into the body to provide protection in the event that the body becomes infected by the antigen. Active immunization tends to be longer lasting than passive immunization, since in the active type, in addition to antibodies, specific memory lymphocytes remain in the circulation. In passive immunization, the duration of the protection is the same as the duration of the antibodies in circulation. 22. Why is maternal milk important for the immune protection of a baby?
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