Johh, her 5-year-old brother, who had survived the same disease and had developed the antibodies (needed / are needed) to combat the illness.

존,그녀의5살짜리남동생, 같은 병에서 살아남았던 그리구, 발전시켜왔던 항체를 (어떤항체?) 필요로 되는항체그질병과 싸우기 위해.

이렇게 되야하니 답은 are needed 같은데 왜,,,,needed 인가요 ㅠ?