EN
The first time you're exposed to a pathogen,
| how long does it take to "mount the defense"?

First line defense take 4 to 5 days and second line of defense takes days or even weeks for new or first time pathogen exposure.

Explanation:

Our immune system has two types of immune resposnes Innate immune system and adaptive immune system.

Innate immune systme is non-specific and act as first line of defense against any pathogen that includes repsonses like sneezing, redness or allergy. Passive barriers in innate immune system are the skin, stomach acid and lysozyme in tears and saliva. When a person expose to a pathogen for first tiem or with any new pathogen, it takes 4 to 5 days before clonal expansion is complete and the lymphocytes have differentiated into effector cells.

Adaptive immunity is the second line of defense which include activation of B and T cells and produces emmory cells.it takes place after the innaet immunity hence take more time. When a person epose fisrt time to a pathogen, they will first face innate immune resposne and then after few days or weeks adapative immune repsosne will generate. B cells will take time to recognise new pathogen and hence will delay in T- cell activation.

Hence, to make defense against first time exposure to pathogen will take 4 to 5 ays for innate response nad several days or week for adaptive resposne depending on the pathogen type.

i'm thinking (a) to keep sand in place; ////////////

explanation: a sand fence or sandbreak, like a snow fence, is used to force windblown, drifting sand to accumulate in a desired place. sand fences are employed to control erosion, sand dune stabilization, keep sand off roadways, and to recruit new material in desert areas.