Which extant chordates are postulated to be most like the earliest chordates in appearance?

#Question id: 1982

#Unit 4. Cell Communication and Cell Signaling

These cells are involved in cell-mediated immunity, and they respond to class I MHC molecule-antigen complexes:

#Question id: 1983

#Unit 4. Cell Communication and Cell Signaling

These cells are involved in innate immunity, and a person lacking these cells may have a higher than normal chance of developing malignant tumors:

#Question id: 1984

#Unit 4. Cell Communication and Cell Signaling

Which of the following is a pathway that would lead to the activation of cytotoxic T cells?

#Question id: 1985

#Unit 4. Cell Communication and Cell Signaling

Which of the following is the last line of defense against an extracellular pathogen?

#Question id: 1986

#Unit 4. Cell Communication and Cell Signaling

The following events occur when a mammalian immune system first encounters a pathogen. Which shows the correct sequence in which they occur?

I.   Pathogen is destroyed.

II.  Lymphocytes secrete antibodies.

III. Antigenic determinants from pathogen bind to antigen receptors on lymphocytes.

 IV.  Lymphocytes specific to antigenic determinants from pathogen become numerous.

V.   Only memory cells remain.

#Question id: 1987

#Unit 4. Cell Communication and Cell Signaling

A nonfunctional CD4 protein on a helper T cell would result in the helper T cell being unable to