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:
A
Explanation:
The passage states that leaves have a lot of organs made up of cells while describing plant leaves' organs.
It's not B, because the statement is false.
It's not C because C was focused on only palisade and guard cells leaving the rest of the passage behind
Waste management would be the most difficult to reproduce once it runs out. Thus, option "C" is the answer.
<h3>What is waste management?</h3>
Waste management~ includes the activities and actions required to manage waste from its inception to its final disposal. This includes the collection, transport, treatment, and disposal of waste, together with monitoring and regulation of the waste management process.
For example, Incineration is the process of burning of solid wastes. It is one of the processes of solid waste management. In this process, combustion of organic and inorganic wastes takes place that leads to the formation of ash, heat and flue gases. Ash is composed of inorganic constituents.
The heat generated during this process can be used to generate electricity. The process is carried out by Incinerators. Incinerators does not completely replace landfilling but it reduces the volume of disposal of wastes.
Thus, option "C" is the answer.
To learn more about Waste management click here:
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Answer:
Explanation:
In gene transfer, researchers introduce a foreign gene directly into cancer cells or into surrounding tissue. The goal is that the newly inserted gene will cause the cancer cells to die or prevent cancer cells and surrounding tissue from funneling blood to tumors, depriving them of nutrients they need for survival.
