CD80 is also known as B7. Question is asking if you know that CD28 (T-cells) interacts with B7 (APC) as a co-stimulatory signal to activate the T-cell.

Looks like the picture is demonstrating contact dermatitis (due to her recent use of new hair dye) which is a type IV HSR

I usually remember that B-7 is on the B-cell (an APC)

so page 103 on FA 2020 as everyone else said. the way I remember is : B7 and CD80/86 have three consecutive numbers --> 678! now sing --> "678 bind 28" I know the numbers are mixed up but at least it helps me rule out answer choices.

FA 2020 pg 103 there's a diagram where you can see binding of B7 protein (CD80/86) ---CD28 as part of T cell activation.

Note: Langerhans cells (LCs) are a specialized subset of dendritic cells (DCs) that populate the epidermal layer of the skin.

History and image are a type 4 HSR. This is T cell induced. Cd40L --> Cd40 is T cell --> B cell CD28 (on T cell) --> binds to APC's (including Langerhans cells); CD80/ 86/ B7

Options with ICAM, I immediately crossed out because they're associated with margination and rolling, etc. CD45 isn't mentioned in regards to T cells (or anywhere I might add). Leaving us with the 2 options I mentioned above ^