In immunology two types of immune response are described depending on whether there is prior contact with the antigen.
• At this first contact, only lymphocytes with receptors specific to the antigen in question are stimulated and lead to the production of antibodies capable of neutralizing it. The lymphocytes capable of recognizing a specific antigen are very few and the production of antibodies - of low intensity and limited duration - is detectable only after a period of latency of several days. This is called the primary response. The specificity of the resulting seropositivity, however, makes it possible to detect contamination (seroconversion).
• Upon re-contact with an antigen that has already triggered a primary response, specific antibody production is found to increase rapidly after a short latency period. The secretion of IgG then reaches levels much higher than those observed during the primary response, while that of IgM is of the same order. This early and intense response, called secondary response, most often results in the destruction of infectious agents before any clinical sign.
• Many centuries before the discovery of microbes, it was noted that people who developed a contagious disease without death were then specifically immunized against the disease, without being protected against others.
• The ability to react appropriately to an already received stimulus supposes the existence of a memory. The immune memory is based on the existence of memory B and T lymphocytes, resulting from the clonal expansion due to the first contact with the antigen. Their lifespan is significantly higher than that of other lymphocytes and their high reactivity gives its rapid and intense character to the secondary response.
Answer:
Gap junctions
Explanation:
Gap junctions form pores that connect adjacent cells. In this way signaling molecules, ions and other substances can pass through the pore to the adjacent cell. This type of cell junctions are important in cardiac muscle responses, in brain signaling, during childbirth, etc.
Answer:
The correct answer is : surveying.
Explanation:
Paleo-anthropology is the study of the extinct primates, it is a sub branch of anthropology. It is focused on the human evolution and rise of the sub type of family of the other human or hominids.
Surveying is the one of paleoanthropoolgy practices that involves the finding the fossils of hominids on the surface of all around the globe by walking to compare it and study the evolution of human family.
Thus, the correct answer is- surveying.
Answer:
the most basic category in the system of taxonomy
