help with some biology questions please

There are two questions in my biology assignment which seems tricky to me, since I have no background:

1. Which of the following two is wrong?

helper T lymphocytes: Stimulate the differentiation and proliferation of B cells and T cells.
dendritic cells: express CD4 and CD8 molecules on the surface.

2. I know IgA is the first line of defense against pathogenic antigens, but IgM is produced first when an antigen is introduced, right? Does IgM count as the first line of defense too?

Thanks

oh god were any of those words

the one about dendritic cells is wrong. cd4 and cd8 are expressed on the surface of T helper and T cytotoxic cells

>>2
What he said.

"IgM antibodies appear early in the course of an infection and usually reappear, to a less extent, after further exposure. IgM antibodies do not pass across the human placenta.

These two biological properties of IgM make it useful in the diagnosis of infectious diseases. Demonstrating IgM antibodies in a patient's serum indicates recent infection, or in a neonate's serum indicates intrauterine infection (e.g. congenital rubella)."

Source is Wikipedia.

I would say that yes it counts as the first line of defense.

Normally the "first line" of defense is considered to be the physical barriers like the skin.  Also non-specific immune system factors like macrophages are part of this.


The second line of defense is the adaptive immune system (anti-bodies, T-cells)

thats wut she sed