Final answer:
Antibodies cannot protect against all illnesses because pathogens can mutate, present new antigens, or be unaffected by antibodies. Clonal selection gives us natural antibodies, but these are not always able to confer lifelong immunity. Our bodies efficiently produce a vast array of antibodies using a limited number of genes, showcasing the immune system's effectiveness.
Step-by-step explanation:
If we have thousands of antibodies, we may still get sick because antibodies cannot protect against all illnesses. While antibodies are highly specific immune proteins that can target particular pathogens, there are various reasons why they might not always provide protection. For instance, pathogens can mutate or present new antigens that the immune system has not yet encountered. Additionally, certain illnesses might be caused by toxins or other factors that antibodies do not affect.
Natural antibodies are present in our bodies due to clonal selection, which is a mechanism that ensures immunity to environmental bacteria and other antigens we encounter. However, the presence of natural antibodies alone is not always sufficient for lifelong immunity, as is the case with colds where the virus mutates frequently making previous antibodies ineffective for new strains.
Regarding the genetic capacity to produce antibodies, the human genome does not need a separate gene for each antibody thanks to the diversity of the variable region of antibodies. This allows for the efficient and effective production of a vast array of antibody molecules despite a limited number of genes, supporting the claim that the human immune system is both effective and efficient.