Connect PC to PC

Hi,
I have two PC’s

First one PC.A, has two NIC’s, NIC.A1 is connecting to company LAN and to the internet, NIC.A2 is connecting with cross-cable to PC.B, which has NIC.B1.

Could you give me some instruction, how to connect right?

So far, I can ping from PC.B both NIC’s in PC.A, but from PC.A I cann’t ping PC.B.

Thanks for your help.