T-cell activation requires antigen being displayed in the context of an APC and interaction between co-stimulatory molecules on the APC and the T cell. In addition to these two signals, T cell activity is often influenced by cytokines. Which of the following is an example of how cytokines can influence T-cell activity in the presence of MHC presentation and costimulatory ligand interaction

A. Antigen-specific TCR binding to MHC peptide
B. Expression of CD4+ or CD8+
C. Interaction with CD80, CD86, or ICOS-L
D. Both A and B
E. Both A and C

Which of the following factors would not contribute to allopatric speciation? a) a population becomes geographically isolated from the parent population. b) the separated population is small, and genetic drift occurs. c) the isolated population is exposed to different selection pressures than the ancestral population. d) different mutations begin to distinguish the gene pools of the separated populations. e) gene flow between the two populations is extensive.

The dense layer of connective tissue that surrounds an entire skeletal muscle is the

What is a difference between systemic and pulmonary circulation? a. systemic circulation carries oxygenated blood to the lungs and pulmonary circulation carries deoxygenated blood to the body. b. systemic circulation carries deoxygenated blood to the lungs and pulmonary circulation carries oxygenated blood to the body. c. systemic circulation carries deoxygenated blood to the body and pulmonary circulation carries oxygenated blood to the lungs. d. systemic circulation carries oxygenated blood to the body and pulmonary circulation carries deoxygenated blood to the lungs.