How does the immune system work together with the circulatory system to function properly?

a.
the immune system's red blood cells fight and destroy foreign antigens.

b.
white blood cells move through the body (to parts where they are needed) in the blood vessels of the circulatory system to destroy pathogens.

c.
the circulatory system's arteries cause the immune system to work harder by bringing oxygen-depleted blood to the infection site.

d.
red blood cells released by immune cells cause increased blood flow to the infection site; this increased blood flow brings other red blood cells to the area more quickly.

Astudy by solloch and et. al., in 2017, gives the map above which shows the frequency of alleles with a ccr5-delta32 mutations over 87 different countries. this mutation deletes the presence of a co-receptor (ccr5) on the outside of human t-cells (lymphocytes). some viruses, such as the one responsible for the black death and human immunodeficiency virus (hiv), require this receptor for attachment to host cells during the infection process. the black death was an epidemic that passed over northern europe during the 14th century killing nearly 60% of europeans. according to this information, which explanation best explains why northern europeans show a greater immunity for hiv than some other parts of the world?

How do the sperm cells get from the stigma to the ovules?

What type of bonds link individual amino acids together?