Blocking antibodies have a variety of functions on the merozoite form of parasitic malaria. While in the merozoite form, malaria parasites invade erythrocytes and reproduce in them. Some blocking antibodies may inhibit the invasion of erythrocytes, while other blocking antibodies prevent the binding of inhibitory antibodies, allowing merozoite invasion of erythrocytes despite the presence of inhibitory antibodies. The monoclonal antibodies that prevent the invasion of merozoites bind to the parasitic antigen MSP-1 (merozoite surface protein 1). The binding of blocking antibodies to MSP-1 is shown to result in the inhibition of secondary processing, resulting in the inability for merozoites to invade host erythrocytes. Secondary processing involves a single proteolytic cleavage on the merozoite surface of the carboxy-terminal component of MSP-1. The blocking of MSP-1 has been proposed to be a method of creating a vaccine against malaria by preventing its invasion and multiplication.