This video, we're going to talk a little bit about cell lysis of invading microbes, which is one of the effects of complement system activation. And so multiple complement system proteins can form a complex in cell membranes, and these complexes are referred to as membrane attack complexes. And so membrane attack complexes are commonly abbreviated as MACs. And so these membrane attack complexes or MACs consist of multiple complement system proteins that create pores or holes in the cell. And these pores or holes in the cell membrane can cause microbes to die by cell lysis. Now these membrane attack complexes or MACs are very effective against gram-negative bacteria, but they are not very effective against gram-positive bacteria because they have a thick peptidoglycan cell wall that surrounds their membrane. However, the gram-negative cells, recall, have an outer lipid membrane, and the membrane attack complex can affect that outer lipid membrane. Now the components of the complement system that are involved in the MAC formation or involved in the membrane attack complex formation include the complement system protein C5 through C9. And so if we take a look at our image down below over here on the left-hand side, once again we're showing you our map of the lesson here that's starting with C3 convertase, which we know results from the activation of the complement system. And the formation of C3 convertase can ultimately lead to one of these three immune responses. And here in this video, we're focusing on microbe cell lysis.

And so cell lysis of invading microbes occurs when complement system proteins form a MAC or MAC, which is a membrane attack complex. And so notice here, we're showing you a microbe. And zooming in, to this microbe, notice that there is a pore here that's being formed by this membrane attack complex or MAC. And notice that the membrane attack complex consists of multiple complement system proteins from C5 through C9, and you can see those complement system components right here. But ultimately, the formation of a membrane attack complex in these gram-negative bacteria can lead to cell lysis of the microbe, and cell lysis of the microbe can eliminate that microbe and prevent it from causing us harm. And so once again, this is one of the effects of activation of the complement system. And so this here concludes our brief lesson on this topic, and we'll be able to get some practice applying these concepts as we move forward. And then we'll get to talk about the third effect of complement system activation which is the inflammatory response. So I'll see you all in our next video.